Summary of the Climate of Walla Walla, Washington
by Robin Rousu
 

The Blue Mountains in spring (first picture) and winter (second picture)

All data originally measured at the Walla Walla Regional Airport, at an elevation of 1,204 ft and located at N46º05'40", W118º17'17".

Mean annual temperature:
47.6º F

Mean annual minimum temperature (average daily low temperature for a whole year):
35.9º F

Mean annual maximum temperature (average daily high temperature for a whole year):
59.3º F
 
Temperature (°F) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
mean maximum 35.5 41.6 49.8 58.4 67.0 75.4 83.5 82.6 72.7 58.9 42.9 36.3
monthly mean 30.0 34.6 40.1 46.2 52.9 60.0 65.1 64.7 57.2 47.4 37.1 31.1
mean minimum 24.5 27.7 30.5 34.0 38.8 44.6 46.7 46.7 41.7 36.0 30.9 25.8

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Average annual precipitation total:
19.53 inches

Median date of last occurrence in spring of
24º F: March 19
28º F: April 19
32º F: May 19
36º F: June 8

Median date of first occurrence in fall of
24º F: November 16
28º F: October 17
32º F: October 2
36º F: September 12

Growing Season:
Average days between occurrences of
24º F: 243
28º F: 183
32º F: 121
36º F: 100

Mean number of days per year with 0.01 inches or more precipitation:
106

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Precipitation (inches) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Sep
monthly precipitation 2.18 1.97 1.94 1.71 1.62 1.09 0.54 0.78 0.98 1.55 2.65 2.52

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Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
mean days w/at least 0.01" precipitation
13
11
12
9
9
7
3
3
5
9
11
12

Mean percentage of possible sunshine:
60%
 
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
mean percentage sky cover 81 74 63 54 50 45 24 27 40 52 74 84
The mean percentage of sky cover is calculated as the amount of clear sky versus the area of sky that is covered in clouds. Measurements are taken only during daylight hours.
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Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
fastest wind (MPH) 42 47 62 41 32 37 36 26 51 54 67 47

Mean sea level pressure:
30.03 inches
 
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
mean sea level pressure (inches) 30.12 30.09 30.03 30.00 29.97 29.94 29.94 29.97 30.06 30.15 30.12 30.03

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Mean annual number of days that the maximum temperature is 90º F or above:
37

Mean annual number of days that the minimum temperature is 32º F or below:
66
 
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
avg highest monthly high (°F) 54.18 59.24 64.88 76.71 84.88 90.24 97.82 97.59 88.12 77.59 60.71 54.94
avg lowest monthly low (°F) 13.06 12.00 26.25 33.94 38.19 44.56 49.94 51.25 40.63 31.63 22.19 12.50
 
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
max temperature 90° F or above
0
0
0
0
1.75
6.50
15.81
13.81
4.50
0
0
0
min temperature Below 32° F
18.88
12.94
4.56
0.19
0
0
0
0
0.06
1.50
7.94
20.38

Average inches of snowfall per year:
17.63 in
 
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
average snowfall (inches) 5.73 4.23 1.33 0.00 0.00 0.00 19.32 0.00 0.00 0.13 2.03 5.86
Mean Relative Humidity (Percent) 7am 1pm 7pm
Annual 70 51 51
January 82 73 80
April 69 44 43
July 54 29 24
October 72 50 54
 

Resources

Environmental Data Service, 1968, Climatic atlas of the United States: U.S. Department of Commerce: Environmental Science Services Administration.

Taylor, G.H. and R.R. Hatton, 1999, The Oregon weather book: a state of extremes: Corvallis, Oregon State University Press.

Taylor, G.H. and C. Hannon, 1999, The climate of Oregon: from rain forest to desert:
Corvallis, Oregon State University Press.

Taylor, G. H. and A. Bartlett, 1993, The climate of Oregon: climate zone 8, northeast area: Corvallis, Oregon Climate Service, Oregon State University.

Walla Walla Weather, http://www.wrcc.dri.edu/cgi-bin/cliMAIN.pl?wawall.
 

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