AgWeatherNet Summer 2013 Weather Review for Washington

Second Warmest Summer On Record Ends with Warmest August Since 1991

Nic Loyd, Meteorologist, 509-786-9357
Gerrit Hoogenboom, Director, 509-786-9371

Overview
Warm, warmest, and warmer is the best way to characterize the 2013 summer season. Dating back to the spring of 2012, it was the 6th consecutive season featuring near or above average temperatures at Prosser. However, this summer was unusually warm even by recent standards. To place the period into context, the +2.1 degree departure from normal was the largest positive seasonal anomaly to occur in more than 10 years (winter of 2002/2003). Overall, it was the second warmest summer on record, and featured particularly warm readings at night. June was generally balmy in spite of the rainfall in eastern Washington late in the month. July was hot and dry, as Prosser recorded the warmest monthly average high temperature (92.1 degrees) on record, while Mt. Vernon experienced only its second rain-free month. Meteorological highlights of the summer included 0.75 inches of rain at Prosser on June 18th, and a high of 108 degrees at Benton City on July 1st. The early July heat wave was the most severe in four years, and also the earliest major hot spell since 1992.

Aside from cool and somewhat unsettled weather during the first few days of August, most of last month was hot and typically dry. There were several minor episodes of isolated showers and thunderstorms sprinkled throughout the month which combined to bring at least light rainfall to most of the state. The most interesting weather events were the isolated and brief torrential downpours that periodically affected various locations during the month. A strong thunderstorm on August 1st dumped an incredible 0.63 inches of rain at East Wenatchee in just 15 minutes, while another storm on August 10th caused 0.79 inches of rain to fall at WSU Sunrise (near Wenatchee) in a 15 minute period. The rain-cooled high temperature of only 59 degrees at Green Bluff on August 2nd gave way to rapidly climbing temperatures thereafter. Hundred Circles reached 100 degrees just four days later on August 6th. The low temperature of 37 degrees at Pullman on the 21st was one of the few cool temperatures recorded during the entire summer.

Human and lightning caused fires plagued the state for much of the month, although weak weather systems at month's end helped to disperse the smoke and improve regional air quality. The first widespread soaking rainfall in 2 months graced western Washington on August 28th/29th, and delivered a much-needed 0.89 inches at Poulsbo South on the 29th. Unfortunately, more moisture was needed before the threat of fires would wane for the season across Washington. Overall, August low temperatures were the warmest on record at Prosser, thanks to an unusually warm air mass and periodically humid weather.

August 2013 Average Temperatures (°F)
Location (Period of Record) Maximum Anomaly Minimum Anomaly Mean Anomaly Soil Temperature
8 inches
Prosser (WSU IAREC; 1989-2013)
87.8
1.3
57.8
3.6
72.6
2.3
72.6
Moxee (1989-2013)
87.7
1.2
51.9
4.1
69.2
1.8
72.7
Mt. Vernon (WSU NWREC; 1994-2013)
75.1
1.8
54.5
2.1
63.9
1.6
64.4
Wenatchee (WSU TFREC; 1994-2013)
87.9
0.7
61.3
2.8
74.6
1.6
79.1
Tri-Cities (1995-2013)
91.2
1.5
60.9
2.1
76.4
1.8
84.8
Walla Walla (1993-2013)
88.8
2.5
60.7
2.2
74.5
1.9
82.4
Moses Lake (1989-2013)
87.2
0.9
57.7
2.7
72.3
1.4
78.4
Omak (Pogue Flat; 2005-2013)
86.3
NA
59.8
NA
72.5
NA
75.7
Royal City East (2008-2013)
85.5
NA
60.6
NA
72.3
NA
77.8
Pullman (2008-2013)
74.1
NA
48.2
NA
67.2
NA
70.1
Long Beach (WSU Long Beach; 2005-2013)
67.1
NA
53.5
NA
59.5
NA
61.8
Sequim (2008-2013)
71.9
NA
51.2
NA
61.1
NA
61.6
Seattle (2011-2013)
78.4
NA
58.2
NA
67.4
NA
72.7
Vancouver (WSU RE; 2008-2013)
79.8
NA
57.3
NA
68.1
NA
67.3
2013 Rainfall and Evapotranspiration (ET) (inches)
Location (Period of Record) Rainfall ET Net
August 2013 August (Rain - ET)
Prosser (WSU IAREC; 1989-2013)
0.13
4.08
7.96
-7.83
Moxee (1989-2013)
0.18
3.50
6.45
-6.27
Mt. Vernon (WSU NWREC; 1994-2013)
1.34
19.08
4.44
-3.10
Wenatchee (WSU TFREC; 1994-2013)
0.66
5.64
6.75
-6.09
Tri-Cities (1995-2013)
0.20
2.79
8.40
-8.20
Walla Walla (1993-2013)
0.15
7.49
7.13
-6.98
Moses Lake (1989-2013)
0.64
3.99
7.40
-6.76
Omak (Pogue Flat; 2005-2013)
1.00
6.22
6.85
-5.85
Royal City East (2008-2013)
0.48
3.07
6.96
-6.48
Pullman (2008-2013)
0.25
7.96
8.05
-7.80
Long Beach (WSU Long Beach; 2005-2013)
2.06
31.98
3.12
-1.06
Sequim (2008-2013)
0.43
6.47
4.48
-4.05
Seattle (2011-2013)
0.91
13.16
4.74
-3.83
Vancouver (WSU RE; 2008-2013)
0.85
16.41
5.77
-4.92
August 2013 Daily Rainfall Time Series Graph for Prosser August 2013 Daily Rainfall Time Series Graph for Long Beach

August Weather
Early August-From Cool and Unsettled to Hot and Dry
August began with very unusual summer conditions, as an upper level low pressure area spun slowly over the region. The resultant weather impacts included thunderstorms with heavy rain and gusty wind, as well as very cool high temperatures, especially relative to the rest of the summer. An incredible convective downpour led to 0.63 inches of rain at East Wenatchee in only 15 minutes during the late afternoon of the 1st. Of the total 1.21 inches of daily rainfall, most of it fell in less than an hour. However, the isolated nature of the event meant that some nearby areas received little to no rain! High temperatures only reached the 70s on August 1st in much of eastern Washington. More rain fell on the 2nd, with 0.88 inches falling at Green Bluff, north of Spokane. Cool day-time temperatures were highlighted by the daily maximum of only 59 degrees at Green Bluff, as many eastern areas peaked in the 60s. August 3rd was a warmer but still pleasant day. Though most areas were dry on August 4th, thunderstorms blossomed in the afternoon over the North Cascades and some adjacent east slope areas. Wenatchee Heights received a downpour of 0.45 inches in 15 minutes, and a daily total of 0.86 inches. Increasingly dry and warm conditions returned for the next week. High temperatures reached 100 degrees at Hundred Circles on August 6th, as low temperatures continued to range from the 40s to the 70s east of the Cascades.

Mid August-Stormy, Then Warm and Dry
Dynamic weather returned on the 9th and 10th in the form of scattered thunderstorms. Numerous sites east of the Cascades observed 15 minute periods of greater than a quarter inch of rainfall. In fact, late on August 10th, WSU Sunrise (south of Wenatchee) recorded an unprecedented 0.79 inches of rainfall in only 15 minutes. Otherwise, warm and dry weather was the rule for much of mid August, with many eastern areas climbing consistently into the 80s to mid 90s during the day.

Late August-Variable Weather
One of the few chilly mornings of the month occurred on the 21st, as the temperature at Pullman dropped to 37 degrees. Active weather made a comeback on August 25th, as an area of rainfall and embedded downpours passed through Washington. Finley observed a station record 0.21 inches of rainfall in 15 minutes. Many areas observed strong winds as well. The maximum gust was 48 mph at Mesa SE. Cloudy skies on August 26th held high temperatures in the 70s in the northern parts of eastern Washington. Light rain fell across much of western Washington on August 27th, with 0.18 inches recorded at Mt. Vernon. Rainfall continued on the 28th in western areas, including 0.39 inches at Puyallup. However, dry conditions and warm temperatures were the rule in eastern Washington, with readings as warm as 94 degrees at Roosevelt. Rain and muggy conditions persisted on August 29th in western areas. Poulsbo South, East Olympia, and WSU Puyallup all received more than 0.8 inches of much-needed rainfall, while Malott (near Omak) received nearly one half-inch.

August 2013 Daily Temperatures
2013 Temperature Time Series Graph for Prosser 2013 Temperature Time Series Graph for Moxee
2013 Temperature Time Series Graph for Wenatchee 2013 Temperature Time Series Graph for Tri-Cities
2013 Temperature Time Series Graph for:Walla Walla August 2013 Temperature Time Series Graph for WSU
August 2013 Temperature Time Series Graph for WSU MosesLake August 2013 Temperature Time Series Graph for WSU Omak
August 2013 Temperature Time Series Graph for WSU Long Beach August 2013 Temperature Time Series Graph for WSU Mt. Vernon

August-By The Numbers
The average August temperature at Prosser (WSU IAREC) was 72.6°F, which is 2.3 degrees (1.4 standard deviations) above average. The average high temperature was 87.8°F, which is 1.3 degrees above average. The average low temperature was 57.8°F, which is 3.6 degrees (1.7 standard deviations) above average. The maximum temperature recorded last month was 95.6°F on August 6th, while the coolest daily high was 73.7°F on August 2nd. Low temperatures ranged from 64.8°F on August 16th to 52.4°F on August 21st. Daily average temperatures ranged from 77.6°F on the 6th to 65.6°F on the 2nd. The monthly precipitation total was 0.13 inches. The average wind speed was 3.6 mph, and the average 8 inch soil temperature was 72.6°F. Wenatchee (WSU TFREC) recorded an average temperature of 74.6°F, which is 1.6 degrees above average, while Walla Walla's average monthly temperature of 74.5°F was 1.9 degrees above average. Pullman was one of the cooler spots in eastern Washington, with an average August temperature of 67.2°F. In western Washington, Mt. Vernon's average temperature was 63.9°F, which is 1.6 degrees above average.


Notable August Events
  • August 1st: 1.21 inches of rain fell at East Wenatchee.
  • August 2nd: The high temperature at Green Bluff reached only 59 degrees.
  • August 6th: The high temperature at Hundred Circles reached 100 degrees.
  • August 10th: An incredible 0.79 inches of rain fell at WSU Sunrise in only 15 minutes.
  • August 21st: The temperature at Pullman dropped to a chilly 37 degrees.
  • August 25th: The wind at Mesa SE gusted to 48 mph.

August Temperature Extremes (°F)
  Observed in 2013 Record Monthly Extremes
Site (Period of Record) Warmest Date Coldest Date Warmest Date Coldest Date
Prosser (WSU IAREC; 1989-2013)
95.6
8/6/2013
52.4
8/21/2013
102.2
8/14/1992
38.5
8/31/2008
Moxee (1989-2013)
94.4
8/7/2013
45.4
8/21/2013
102.8
8/1/2009
32.4
8/31/2008
Mt. Vernon (WSU NWREC; 1994-2013)
80.6
8/16/2013
44.9
8/21/2013
89.8
8/29/1996
40.6
8/28/2010
Wenatchee (WSU TFREC; 1994-2013)
98.4
8/9/2013
51.2
8/31/2013
106.4
8/17/2008
42.2
8/28/2000
Tri-Cities (1995-2013)
99.7
8/6/2013
53.8
8/21/2013
106.8
8/4/1998
45.5
8/25/2012
Walla Walla (1992-2013)
96.4
8/6/2013
50.8
8/21/2013
106.1
8/4/1998
42.2
8/4/1992
Moses Lake (1989-2013)
95.1
8/9/2013
47.9
8/21/2013
104.7
8/4/1998
39.4
8/23/1992
Omak (Pogue Flat; 2005-2013)
95.2
8/9/2013
53.7
8/30/2013
104.0
8/17/2008
40.2
8/31/2006
Royal City East (2008-2013)
94.1
8/7/2013
55.5
8/26/2013
101.4
8/17/2008
42.9
8/31/2008
Pullman (2008-2013)
95.4
8/14/2013
37.3
8/21/2013
102.2
8/17/2008
32.0
8/25/2012
Long Beach (WSU Long Beach; 2005-2013)
74.0
8/31/2013
43.3
8/13/2013
94.7
8/14/2010
39.5
8/31/2010
Sequim (2008-2013)
82.9
8/22/2013
42.5
8/22/2013
87.0
8/15/2010
36.4
8/23/20103
Seattle (2011-2013)
87.0
8/6/2013
51.2
8/21/2013
NA
NA
NA
NA
Vancouver (WSU RE; 2008-2013)
89.2
8/6/2013
50.5
8/13/2013
100.6
8/4/2012
40.1
8/31/2008

Summer Weather
June and July Review
June was fairly warm, but wet at times later in the month in eastern Washington. Moxee's average low temperature was 4.2 degrees above average, and the warmest since 1992. Overall, statewide temperatures were 1 to 2 degrees above average for the month, despite some cool daytime temperatures later in June in rainy eastern areas. Highlights for the month included 0.75 inches of rain at Prosser on June 18th, 1.3 inches of rain at Green Bluff on June 20th, and 100 degree temperatures in central Washington on the 30th. Unfortunately, cracking was a concern for many cherry growers in central Washington in late June.

July was characterized by extreme heat in the east, as well as extreme dryness in western areas. The heat wave on July 1st and 2nd sent temperatures soaring as high as 108 degrees in central Washington, with lows warmer than 80 degrees in some spots. It was the warmest weather in four years, and the earliest heat wave of that magnitude since 1992. In terms of day-time temperatures, July was the warmest month on record (1990 to present) at Prosser, with an average high of 92.1 degrees. Though overnight lows were above average to a lesser degree, it was still the second warmest month on record at Prosser, behind only July 1998. Many locations west of the Cascades received no rainfall during July, and Mt. Vernon experienced only its second precipitation free month on record. Not surprisingly, large fires and smoky skies were the main concerns during July.

Winter 2013 Daily Rainfall Time Series Graph for Prosser Winter 2013 Daily Rainfall Time Series Graph for Long Beach

Summer-By The Numbers
The average summer temperature at Prosser (WSU IAREC) was 71.5°F, which is 2.1 degrees (1.4 standard deviations) above average. The average high temperature was 86.3°F, which is 1.9 degrees (1 standard deviation) above average, while the average low temperature was 55.7°F, which is 2.5 degrees (1.7 standard deviations) above average. Daily high temperatures ranged from 102.0°F on July 2nd to 62.1°F on June 18th. Low temperatures varied from 68.5°F on July 2nd to 41.5°F on June 12th. Daily average temperatures ranged from 85.3°F on July 2nd to 57.9°F on June 12th. 1.71 inches of rain fell during the summer season. The average wind speed was 3.8 mph, while the average 8 inch soil temperature was 72.3°F. Other locations also experienced above normal summer temperatures. Wenatchee (WSU TFREC) had an average seasonal temperature of 74.0 °F, which is 2.4 degrees above average. Overall, the summer of 2013 was 2.1 degrees warmer than last summer at Prosser (WSU IAREC).

Summer 2013 Average Temperatures (°F)
Location (Period of Record) Maximum Anomaly Minimum Anomaly Mean Anomaly Soil Temperature
8 inches
Prosser (WSU IAREC; 1989-2013)
86.3
1.9
55.7
2.5
71.5
2.1
72.3
Moxee (1989-2013)
86.4
2.1
50.7
3.0
69.3
2.1
70.2
Mt. Vernon (WSU NWREC; 1994-2013)
73.3
2.3
52.8
1.2
62.3
1.4
64.0
Wenatchee (WSU TFREC; 1994-2013)
86.8
2.0
60.4
2.8
74.0
2.4
77.4
Tri-Cities (1995-2013)
89.7
2.0
58.8
1.1
75.1
1.7
83.2
Walla Walla (1993-2013)
86.5
3.0
58.7
1.8
72.6
2.0
79.4
Moses Lake (1989-2013)
85.6
1.6
55.9
1.8
71.7
1.5
76.2
Omak (Pogue Flat; 2005-2013)
84.7
NA
58.1
NA
71.5
NA
73.2
Royal City East (2008-2013)
84.3
NA
58.0
NA
70.8
NA
76.3
Pullman (2008-2013)
80.2
NA
46.8
NA
64.8
NA
68.2
Long Beach (WSU Long Beach; 2005-2013)
65.2
NA
51.9
NA
58.3
NA
61.4
Sequim (2008-2013)
70.5
NA
50.2
NA
60.2
NA
60.4
Seattle (2011-2013)
76.7
NA
56.1
NA
65.7
NA
71.1
Vancouver (WSU RE; 2008-2013)
77.8
NA
55.0
NA
65.9
NA
66.3
Summer 2013 Rainfall and Evapotranspiration (ET) (inches)
Location (Period of Record) Rainfall ET Net
(Rain - ET)
Prosser (WSU IAREC; 1989-2013)
1.71
26.31
-24.60
Moxee (1989-2013)
0.40
23.92
-23.52
Mt. Vernon (WSU NWREC; 1994-2013)
2.61
15.13
-12.52
Wenatchee (WSU TFREC; 1994-2013)
1.74
24.28
-22.54
Tri-Cities (1995-2013)
0.93
28.35
-27.42
Walla Walla (1993-2013)
1.83
22.81
-20.98
Moses Lake (1989-2013)
2.34
24.98
-22.64
Omak (Pogue Flat; 2005-2013)
2.27
24.04
-21.77
Royal City East (2008-2013)
1.63
23.84
-22.21
Pullman (2008-2013)
2.58
24.29
-21.71
Long Beach (WSU Long Beach; 2005-2013)
4.29
10.81
-6.52
Sequim (2008-2013)
0.97
15.73
-14.76
Seattle (2011-2013)
2.40
15.98
-13.58
Vancouver (WSU RE; 2008-2013)
2.82
19.63
-16.81
Notable Summer Events
  • June 18th: 0.75 inches of rain fell at Prosser (WSU IAREC).
  • June 20th: 1.3 inches of rain fell at Green Bluff, as the high reached only 49 degrees.
  • July 1st: The temperature at Benton City soared to a scorching 108 degrees.
  • July 2nd: The low temperature at Wallula was a sultry 81 degrees.
  • July 13th: The temperature at LaCrosse dropped to 37 degrees.
  • August 29th: 0.89 inches of rain fell at Poulsbo South.

Summer Temperature Extremes (°F)
  Observed in 2013 Record Seasonal Extremes
Site (Period of Record) Warmest Date Coldest Date Warmest Date Coldest Date
Prosser (WSU IAREC; 1989-2013)
102.0
7/2/2013
41.5
6/12/2013
109.9
7/12/2002
35.3
6/6/1999
Moxee (1989-2013)
102.6
7/2/2013
36.3
6/12/2013
107.5
7/12/2002
29.2
6/6/1999
Mt. Vernon (WSU NWREC; 1994-2013)
84.1
6/30/2013
44.9
8/21/2013
96.1
7/29/2009
40.0
6/2/1999
Wenatchee (WSU TFREC; 1994-2013)
104.0
7/2/2013
46.0
6/15/2013
106.6
7/23/2006
40.0
6/8/2012
Tri-Cities (1995-2013)
107.9
7/1/2013
46.0
6/12/2013
110.1
7/23/2006
40.9
6/2/2001
Walla Walla (1992-2013)
103.1
7/2/2013
46.1
6/1/2013
107.3
7/12/2002
37.9
6/7/1995
Moses Lake (1989-2013)
101.4
7/1/2013
44.4
6/15/2013
107.8
7/23/2006
37.8
6/8/2002
Omak (Pogue Flat; 2005-2013)
100.5
7/2/2013
44.8
6/14/2013
105.5
7/23/2006
35.4
6/7/2012
Royal City East (2008-2013)
100.6
7/2/2013
44.0
6/12/2013
101.4
8/17/2008
40.3
6/16/2010
Pullman (2008-2013)
95.7
7/2/2013
35.8
6/1/2013
102.2
8/17/2008
31.2
7/11/2008
Long Beach (WSU Long Beach; 2005-2013)
75.1
7/16/2013
42.3
6/15/2013
95.5
7/7/2010
36.9
6/12/2007
Sequim (2008-2013)
85.0
6/30/2013
38.9
6/15/2013
91.8
7/28/2009
32.8
6/30/2009
Seattle (2011-2013)
92.2
6/30/2013
46.6
6/10/2013
NA
NA
NA
NA
Vancouver (WSU RE; 2008-2013)
93.9
6/30/2013
44.8
6/1/2013
104.1
7/29/2009
39.6
6/6/2012
Weather Summary By Month
  • June: Generally above normal temperatures, and wet in parts of eastern Washington.
  • July: Record heat in the east, and record dryness in the west.
  • August: Above normal temperatures and variable rainfall.

Agriculture Report
As of August 25th, the winter wheat harvest was 90% complete, while seeding for next year was just beginning. Potato harvest continued in Walla Walla County, and Thurston County Christmas tree growers sheared trees for sale this year. In central Washington, gala apple harvest began, with reports of good yield and quality. In Whatcom County, harvest of most berry varieties was nearing completion. On August 10th, thunderstorms north of Wenatchee caused hail damage on some trees, while strong winds blew fruit off of the trees. Though unsettled weather early in the month slowed field work slightly, much of the month was warm and dry, with only a few periods of scattered showers and thunderstorms. However, the most significant rain of the month for western Washington came on August 28/29, with daily values approaching one inch in places. By the end of the month, the Yakima Valley Bartlett pear harvest neared completion, while Gala apple harvest continued, and early hop harvest began (National Agricultural Statistics Service).

April 1 to August 31 Accumulated Growing Degree Days
  Base Temperature (°F)
32 43 50
Location 2013 5 Year Avg Difference 2013 5 Year Avg Difference 2013 5 Year Avg Difference
Prosser (WSU IAREC)
5058
4721
337
3376
3045
331
2358
2050
308
Tri-Cities
5454
5177
277
3771
3495
276
2739
2469
270
Walla Walla
5194
4873
321
3515
3194
321
2504
2190
314
Wenatchee (WSU TFREC)
5321
5019
302
3638
3341
297
2621
2337
284
Moxee
4638
4287
351
2976
2634
342
2015
1704
311
Omak (Pogue Flat)
4996
4718
278
3318
3049
269
2335
2083
252
Moses Lake
4965
4756
209
3289
3082
207
2289
2091
198
Pullman
3917
3712
205
2305
2097
208
1408
1237
171
Royal City East
5059
4743
316
3377
3065
312
2366
2075
291
Mt. Vernon (WSU NWREC)
4095
3809
286
2413
2128
285
1403
1142
261
Long Beach (WSU Long Beach)
3570
3370
200
1888
1694
194
908
755
153
Sequim
3712
3418
294
2034
1755
279
1070
850
220

GDD are calculated by subtracting a base temperature from the average daily temperature (°F). If the resulting value is less than 0, then it is set to 0. Thus GDD are always 0 or greater.

GDD = (Tmax+Tmin)/2 - Tbase


This Month in History
On August 31st, 2008, the temperature at Moxee plunged to a monthly record low of 32.4 degrees.

Climate Outlook
According to the Climate Prediction Center (CPC), above average temperatures are expected in September, especially in the east, along with near average rainfall across the state. Later in the autumn, near average temperatures are most likely, along with enhanced odds for above average precipitation in eastern Washington.

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