AgWeatherNet Summer 2015 Weather Review for Washington

Hottest Summer on Record Ends with Autumn-Like Storm

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

Overview
The already historic summer of 2015 ended with a meteorological curveball from Mother Nature, as a season of record heat concluded with a powerful, autumn-like storm. However, perhaps the major pattern change should not have been surprising, since such long-term environmental imbalances sometimes require a rapid course correction to facilitate a shift toward system equilibrium.

2015 was Prosser's hottest summer ever, as last year's record was shattered by more than one degree. The seasonal mean temperature was 3.7 degrees above normal, which is due mainly to the fact that June was by far the hottest calendar month (relative to normal) on record. June was actually warmer than August in 2015, which is only the second time that this has occurred. On June 28th, PK_McClenny reached a scalding 114 degrees during the second major heat wave of that month. By contrast, August was merely somewhat above normal, and pales in comparison to June and even July. The summer of 2015 is tied for the most above normal season on record, which is rather unusual given that winter tends to be a more variable season from year to year. Overall, the summer was hot, smoky, and dry.

Luckily, everything changed on Saturday, August 29th. The potent low pressure system that featured wind, rain, and cooler temperatures was notably strong for any Washington storm, but was especially impressive given the typically inactive and benign time of year, and was even more remarkable given the oppressive monotony of 2015 to that point. The regrettable impacts of the strong wind included power outages, blowing dust, and road closures. However, the merciful rainfall and cooling temperatures were welcomed by firefighters, and the air mass exchange helped to clear the smoke and improve the air quality.

A highlight of the storm included Anatone recording a 52.5 mph wind gust, which was their strongest since June 2008, and the strongest recorded at any AgWeatherNet station since May. Meanwhile, Tumwater SW recorded 1.4 inches of rain on August 29th, which was their highest daily total since March 15th, while East Olympia recorded a 15 minute rain value of 0.24 inches. At Pogue Flat (Omak), the high temperature on August 31st of 66.4 degrees was their coolest high (at that time) since May 13th. Despite the radical pattern change and unusually strong summer storm in late August, the headline of the season was certainly the unrelenting and largely unprecedented heat.

August 2015 Average Temperatures (°F)
Location (Period of Record) Maximum Anomaly Minimum Anomaly Mean Anomaly Soil Temperature
8 inches
Prosser (WSU IAREC; 1989-2015)
87.1
0.5
55.6
1.2
71.0
0.6
72.5
Moxee (1989-2015)
NA
NA
NA
NA
NA
NA
66.5
Mt Vernon (WSU NWREC; 1994-2015)
75.6
2.1
53.4
0.9
64.3
1.8
65.8
Wenatchee (WSU TFREC; 1994-2015)
88.6
1.3
61.1
2.3
75.1
1.9
79.7
Tri-Cities (1995-2015)
91.6
1.7
60.4
1.3
76.1
1.3
84.2
Walla Walla (1993-2015)
88.5
2.0
59.9
1.2
74.1
1.3
81.1
Moses Lake (1989-2015)
88.0
1.5
56.5
1.3
72.1
1.1
80.6
Omak (Pogue Flat; 2005-2015)
86.8
NA
58.6
NA
72.7
NA
77.2
Royal City East (2008-2015)
85.5
NA
59.5
NA
71.7
NA
78.6
Pullman (2008-2015)
83.9
NA
49.3
NA
68.0
NA
72.5
Long Beach (WSU Long Beach; 2005-2015)
70.3
NA
52.3
NA
61.0
NA
67.2
Sequim (2008-2015)
75.0
NA
51.2
NA
62.9
NA
64.4
Seattle (2011-2015)
78.7
NA
57.3
NA
67.1
NA
73.2
Vancouver (WSU RE; 2008-2015)
82.3
NA
55.2
NA
69.0
NA
69.7
2015 Rainfall and Evapotranspiration (ET) (inches)
Location (Period of Record) Rainfall ET Net
August 2015 August (Rain - ET)
Prosser (WSU IAREC; 1989-2015)
0.00
3.61
8.05
-8.05
Moxee (1989-2015)
0.00
2.62
5.24
-5.24
Mt. Vernon (WSU NWREC; 1994-2015)
1.46
14.43
5.25
-3.79
Wenatchee (WSU TFREC; 1994-2015)
0.07
4.44
8.20
-8.13
Tri-Cities (1995-2015)
0.00
3.72
9.16
-9.16
Walla Walla (1993-2015)
0.36
7.97
7.16
-6.80
Moses Lake (1989-2015)
0.00
2.90
8.63
-8.63
Omak (Pogue Flat; 2005-2015)
0.13
3.46
6.59
-6.46
Royal City East (2008-2015)
0.00
2.30
7.90
-7.90
Pullman (2008-2015)
0.09
8.57
9.72
-9.63
Long Beach (WSU Long Beach; 2005-2015)
0.58
23.94
3.79
-3.21
Sequim (2008-2015)
0.57
8.35
4.91
-4.34
Seattle (2011-2015)
3.43
17.42
5.00
-1.57
Vancouver (WSU RE; 2008-2015)
1.34
16.49
6.62
-5.28
May 2015 Daily Rainfall Time Series Graph for Long Beach

August Weather
Early August-Hot and Dry
Very hot weather at the beginning of the month eventually yielded to more seasonal but still warm conditions. High temperatures in central areas began August in the 90s and 100s, before falling into the 80s by August 5th.

Mid August-Very Warm and Mainly Dry
Very warm temperatures returned early in the period, before strong winds and widespread blowing dust arrived on August 14th. Following a brief mid-month cool down, hot weather resumed later in the period.

Late August-Hot and Dry to Cooler and Stormy
Hot and dry weather for most of the period transitioned to much cooler and unsettled weather during the final 3 or 4 days of August. A potent storm passage on August 29th brought strong winds to Washington, along with locally heavy rain to western areas, while also ushering in a major pattern change.

August 2015 Daily Temperatures
2015 temperature Time Series Graph for Prosser 2015 temperature Time Series Graph for Moxee
2015 temperature Time Series Graph for Wenatchee 2015 temperature Time Series Graph for Tri-Cities
2015 temperature Time Series Graph for:Walla Walla May 2015 Temperature Time Series Graph for WSU
May 2015 Temperature Time Series Graph for WSUMoses Lake May 2015 Temperature Time Series Graph for WSU Omak
May 2015 Temperature Time Series Graph for WSU Long Beach May 2015 Temperature Time Series Graph for WSU Mt. Vernon

August-By The Numbers
The average August temperature at Prosser (WSU IAREC) was 71.0°F, which is 0.6 degrees above average. The average high temperature was 87.1°F, which is 0.5 degrees above average. The average low temperature was 55.6°F, which is 1.2 degrees above average. The maximum temperature recorded last month was 101.7°F on August 1st, while the coolest daily high was 72.8°F on August 30th. Low temperatures ranged from 65.0°F on August 14th to 47.2°F on August 23rd. Daily average temperatures ranged from 80.5°F on the 12th to 63.2°F on the 30th. The monthly precipitation total was 0 inches. The average wind speed was 4.2 mph, and the average 8 inch soil temperature was 72.5°F.


Notable August Events
  • August 1st: The high temperature at Wenatchee rose to 104 degrees.
  • August 7th: The low temperature at Pullman was a chilly 39 degrees.
  • August 12th: The high temperature at the Tri-Cities soared to 104 degrees.
  • August 29th: 1.4 inches of rain fell at Tumwater SW.
  • August 29th: The wind at Anatone gusted to 53 mph.

August Temperature Extremes (°F)
  Observed in 2015 Record Monthly Extremes
Site (Period of Record) Warmest Date Coldest Date Warmest Date Coldest Date
Prosser (WSU IAREC; 1989-2015)
101.7
8/1/2015
47.2
8/23/2015
102.2
8/14/1992
38.5
8/31/2008
Moxee (1989-2015)
NA
NA
39.7
8/23/2015
102.8
8/1/2009
32.4
8/31/2008
Mt. Vernon (WSU NWREC; 1994-2015)
86.7
8/19/2015
46.5
8/26/2015
89.8
8/29/1996
40.6
8/28/2010
Wenatchee (WSU TFREC; 1994-2015)
104.1
8/1/2015
46.8
8/23/2015
106.4
8/17/2008
42.2
8/28/2000
Tri-Cities (1995-2015)
103.9
8/12/2015
52.6
8/23/2015
106.8
8/4/1998
45.5
8/25/2012
Walla Walla (1992-2015)
102.7
8/1/2015
48.7
8/22/2015
106.1
8/4/1998
42.2
8/4/1992
Moses Lake (1989-2015)
101.9
8/1/2015
44.3
8/23/2015
104.7
8/4/1998
39.4
8/23/1992
Omak (Pogue Flat; 2005-2015)
102.8
8/12/2015
46.6
8/23/2015
104.0
8/17/2008
40.2
8/31/2006
Royal City East (2008-2015)
97.4
8/12/2015
52.3
8/6/2015
101.4
8/17/2008
42.9
8/31/2008
Pullman (2008-2015)
99.0
8/13/2015
37.6
8/22/2015
102.2
8/17/2008
32.0
8/25/2012
Long Beach (WSU Long Beach; 2005-2015)
86.0
8/18/2015
42.0
8/24/2015
94.7
8/14/2010
39.5
8/31/2010
Sequim (2008-2015)
87.1
8/11/2015
44.9
8/22/2015
87.1
8/11/2015
36.4
8/23/2010
Seattle (2011-2015)
90.7
8/1/2015
50.2
8/25/2015
NA
NA
NA
NA
Vancouver (WSU RE; 2008-2015)
95.9
8/1/2015
46.1
8/25/2015
100.6
8/4/2012
40.1
8/31/2008

Summer Weather
June and July Review
June was an incredibly warm month. It was by far the hottest calendar month on record, with an unprecedented +8.1 degree departure from normal at Prosser, including +9.6 degrees during the day. Two major heat waves punctuated the scalding temperatures of June. Benton City reached 106 degrees on June 8th, and then PK_McClenny soared to 114 degrees on the 28th.

July was another very hot and dry month, as Mt. Vernon experienced their warmest month on record. Orondo climbed to 109 degrees on July 3rd, while Wahluke Slope recorded a low of 83 degrees. On July 9th, Whitcomb Island concluded a stretch of 14 consecutive days above 100 degrees. Although temperatures were scorching during the first ten days of the month, the heat subsided a bit for mid-July, and 0.83 inches of rain fell at Anatone on the 11th. The end of July was rather changeable. The temperature at Peshastin peaked at 105 degrees on the 19th. However, a cool storm passage sent the high temperature at Pullman down to 66 degrees on the 27th. In fact, July 26th was Prosser's coolest day, relative to normal, since January 2nd. By July 31st, the temperature at Benton City had warmed to 108 degrees.

Winter 2013 Daily Rainfall Time Series Graph for Long Beach

Summer-By The Numbers
The average summer temperature at Prosser (WSU IAREC) was 73.4°F, which is 3.7 degrees (2.2 standard deviations) above average. The average high temperature was 88.8°F, which is 4.1 degrees (2.0 standard deviations) above average, while the average low temperature was 56.8°F, which is 3.3 degrees (1.9 standard deviations) above average. Daily high temperatures ranged from 104.3°F on July 31st to 72.8°F on August 30th. Low temperatures varied from 73.3°F on June 29th to 46.8°F on June 14th. Daily average temperatures ranged from 87.0°F on June 28th to 63.0°F on June 13th. 0 inches of rain fell during the summer season. The average wind speed was 4.2 mph, while the average 8 inch soil temperature was 75.3°F.

Summer 2015 Average Temperatures (°F)
Location (Period of Record) Maximum Anomaly Minimum Anomaly Mean Anomaly Soil Temperature
8 inches
Prosser (WSU IAREC; 1989-2015)
88.8
4.1
56.8
3.3
73.4
3.7
75.3
Moxee (1989-2015)
NA
NA
NA
NA
NA
NA
66.1
Mt. Vernon (WSU NWREC; 1994-2015)
75.9
4.5
53.3
1.5
64.4
3.2
65.4
Wenatchee (WSU TFREC; 1994-2015)
90.3
5.1
62.5
4.5
77.0
5.0
79.6
Tri-Cities (1995-2015)
93.3
5.2
61.9
3.9
78.4
4.6
86.2
Walla Walla (1993-2015)
89.7
5.7
60.8
3.5
75.4
4.5
81.2
Moses Lake (1989-2015)
89.5
5.1
57.9
3.6
74.2
4.4
81.8
Omak (Pogue Flat; 2005-2015)
88.5
NA
59.5
NA
74.5
NA
78.3
Royal City East (2008-2015)
87.3
NA
60.0
NA
73.4
NA
80.0
Pullman (2008-2015)
83.4
NA
49.7
NA
68.0
NA
73.2
Long Beach (WSU Long Beach; 2005-2015)
68.3
NA
51.3
NA
59.8
NA
66.4
Sequim (2008-2015)
74.9
NA
51.1
NA
63.1
NA
63.4
Seattle (2011-2015)
80.0
NA
57.2
NA
68.0
NA
74.2
Vancouver (WSU RE; 2008-2015)
82.7
NA
55.7
NA
69.3
NA
68.7
Summer 2015 Rainfall and Evapotranspiration (ET) (inches)
Location (Period of Record) Rainfall ET Net
(Rain - ET)
Prosser (WSU IAREC; 1989-2015)
0.00
27.71
-27.71
Moxee (1989-2015)
0.00
23.39
-23.39
Mt. Vernon (WSU NWREC; 1994-2015)
2.18
17.69
-15.51
Wenatchee (WSU TFREC; 1994-2015)
0.15
29.31
-29.16
Tri-Cities (1995-2015)
0.00
32.43
-32.43
Walla Walla (1993-2015)
0.45
24.63
-24.18
Moses Lake (1989-2015)
0.03
29.33
-29.30
Omak (Pogue Flat; 2005-2015)
0.37
24.00
-23.63
Royal City East (2008-2015)
0.01
26.66
-26.65
Pullman (2008-2015)
0.47
28.49
-28.02
Long Beach (WSU Long Beach; 2005-2015)
1.05
12.54
-11.49
Sequim (2008-2015)
0.98
17.13
-16.15
Seattle (2011-2015)
3.85
18.30
-14.45
Vancouver (WSU RE; 2008-2015)
2.69
22.42
-19.73
Notable Summer Events
  • June 8th: The temperature at Benton City climbed to 106 degrees.
  • June 13th: The temperature at Ritzville plunged to 31 degrees.
  • June 28th: The temperature at PK_McClenny rose to 114 degrees.
  • June 28th: The low temperature at Wahluke Slope was a sultry 85 degrees.
  • July 3rd: The temperature at Orondo peaked at 109 degrees.
  • July 11th: 0.83 inches of rain fell at Anatone.
  • July 27th: The high temperature at Pullman was only 66 degrees.
  • August 14th: The wind at Pullman gusted to 41 mph.

Summer Temperature Extremes (°F)
  Observed in 2015 Record Seasonal Extremes
Site (Period of Record) Warmest Date Coldest Date Warmest Date Coldest Date
Prosser (WSU IAREC; 1989-2015)
104.3
7/31/2015
46.8
6/14/2015
109.9
7/12/2002
35.3
6/6/1999
Moxee (1989-2015)
NA
NA
39.1
6/13/2015
107.5
7/12/2002
29.2
6/6/1999
Mt. Vernon (WSU NWREC; 1994-2015)
91.5
7/19/2015
42.7
6/13/2015
96.1
7/29/2009
40.0
6/2/1999
Wenatchee (WSU TFREC; 1994-2015)
107.3
6/28/2015
46.8
8/23/2015
107.3
6/28/2015
40.0
6/8/2012
Tri-Cities (1995-2015)
113.1
6/28/2015
50.9
6/14/2015
113.1
6/28/2015
40.9
6/2/2001
Walla Walla (1992-2015)
109.1
6/28/2015
47.7
6/13/2015
109.1
6/28/2015
37.9
6/7/1995
Moses Lake (1989-2015)
105.0
6/28/2015
44.3
8/23/2015
107.8
7/23/2006
37.8
6/8/2002
Omak (Pogue Flat; 2005-2015)
108.7
6/28/2015
41.6
6/13/2015
108.7
6/28/2015
35.4
6/7/2012
Royal City East (2008-2015)
102.1
6/27/2015
49.8
6/4/2015
102.1
6/27/2015
40.3
6/16/2010
Pullman (2008-2015)
101.9
6/28/2015
34.2
6/13/2015
102.2
8/17/2008
31.2
7/11/2008
Long Beach (WSU Long Beach; 2005-2015)
86.7
7/18/2015
39.4
6/17/2015
95.5
7/7/2010
36.9
6/12/2007
Sequim (2008-2015)
88.5
6/27/2015
40.3
6/13/2015
91.8
7/28/2009
32.8
6/30/2009
Seattle (2011-2015)
95.8
7/19/2015
48.8
6/4/2015
NA
NA
NA
NA
Vancouver (WSU RE; 2008-2015)
101.4
7/30/2015
46.1
8/25/2015
104.1
7/29/2009
39.6
6/6/2012
Weather Summary By Month
  • June: Very hot and dry.
  • July: Hot and dry.
  • August: Hot and smoky.

Agriculture Report
Some wind damage was reported in corn fields in Skagit County as a result of the late August storm. Otherwise, apple, peach, and wine grape harvest continued in August. Most of the month was hot, dry, and smoky (National Agricultural Statistics Service).

April 1 to August 31 Accumulated Growing Degree Days
  Base Temperature (°F)
32 43 50
Location 2015 5 Year Avg Difference 2015 5 Year Avg Difference 2015 5 Year Avg Difference
Prosser (WSU IAREC)
5304
4834
470
3622
3159
463
2587
2157
430
Tri-Cities
5900
5328
572
4220
3647
573
3164
2615
549
Walla Walla
5518
4987
531
3839
3309
530
2797
2298
499
Wenatchee (WSU TFREC)
5686
5141
545
4004
3464
540
2975
2456
519
Moxee
4942
4441
501
3269
2781
488
2293
1832
461
Omak (Pogue Flat)
5356
4834
522
3673
3166
507
2670
2193
477
Moses Lake
5386
4908
478
3704
3231
473
2671
2225
446
Pullman
4315
3822
493
2662
2201
461
1733
1329
404
Royal City East
5401
4866
535
3719
3189
530
2686
2190
496
Mt. Vernon (WSU NWREC)
4302
3913
389
2619
2235
384
1592
1243
349
Long Beach (WSU Long Beach)
3681
3427
254
1998
1753
245
1021
810
211
Sequim
4043
3583
460
2360
1914
446
1389
987
402

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 25, 2012, the temperature at Pullman dipped to 32 degrees.

Climate Outlook
According to the Climate Prediction Center (CPC), warmer than normal conditions are likely during the rest of 2015 and well into 2016, while drier than normal weather is somewhat likely for much of the coming autumn and winter. El NiƱo is currently strong, and is expected to peak, possibly at a record level, in the late autumn or early winter.

Washington State University