Average Weather in Walla Walla Washington, United States
In Walla Walla, the summers are short, hot, dry, and mostly clear and the winters are very cold and mostly cloudy. Over the course of the year, the temperature typically varies from 30°F to 93°F and is rarely below 17°F or above 102°F.
Based on the tourism score, the best time of year to visit Walla Walla for warm-weather activities is from early July to early September.
The hot season lasts for 2.7 months, from June 19 to September 10, with an average daily high temperature above 82°F. The hottest day of the year is July 31, with an average high of 93°F and low of 65°F.
The cold season lasts for 3.2 months, from November 15 to February 22, with an average daily high temperature below 50°F. The coldest day of the year is December 29, with an average low of 30°F and high of 40°F.
Average High and Low Temperature
The figure below shows you a compact characterization of the entire year of hourly average temperatures. The horizontal axis is the day of the year, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.
Average Hourly Temperature
In Walla Walla, the average percentage of the sky covered by clouds experiences significant seasonal variation over the course of the year.
The clearer part of the year in Walla Walla begins around June 11 and lasts for 3.9 months, ending around October 8. On July 29, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 82% of the time, and overcast or mostly cloudy 18% of the time.
The cloudier part of the year begins around October 8 and lasts for 8.1 months, ending around June 11. On January 16, the cloudiest day of the year, the sky is overcast or mostly cloudy 68% of the time, and clear, mostly clear, or partly cloudy 32% of the time.
Cloud Cover Categories
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Walla Walla varies significantly throughout the year.
The wetter season lasts 7.3 months, from October 21 to June 1, with a greater than 22% chance of a given day being a wet day. The chance of a wet day peaks at 37% on November 28.
The drier season lasts 4.6 months, from June 1 to October 21. The smallest chance of a wet day is 7% on August 3.
Among wet days, we distinguish between those that experience rain alone, snow alone, or a mixture of the two. Based on this categorization, the most common form of precipitation throughout the year is rain alone, with a peak probability of 32% on November 19.
Daily Chance of Precipitation
To show variation within the months and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day of the year. Walla Walla experiences some seasonal variation in monthly rainfall.
The rainy period of the year lasts for 10 months, from September 2 to July 8, with a sliding 31-day rainfall of at least 0.5 inches. The most rain falls during the 31 days centered around November 22, with an average total accumulation of 2.0 inches.
The rainless period of the year lasts for 1.8 months, from July 8 to September 2. The least rain falls around July 30, with an average total accumulation of 0.3 inches.
Average Monthly Rainfall
We report snowfall in liquid-equivalent terms. The actual depth of new snowfall is typically between 5 and 10 times the liquid-equivalent amount, assuming the ground is frozen. Colder, drier snow tends to be on the higher end of that range and warmer, wetter snow on the lower end.
As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day of the year. Walla Walla experiences some seasonal variation in monthly liquid-equivalent snowfall.
The snowy period of the year lasts for 2.9 months, from November 22 to February 19, with a sliding 31-day liquid-equivalent snowfall of at least 0.1 inches. The most snow falls during the 31 days centered around December 30, with an average total liquid-equivalent accumulation of 0.3 inches.
The snowless period of the year lasts for 9.1 months, from February 19 to November 22. The least snow falls around July 14, with an average total liquid-equivalent accumulation of 0.0 inches.
Average Liquid-Equivalent Monthly Snowfall
The length of the day in Walla Walla varies significantly over the course of the year. In 2018, the shortest day is December 21, with 8 hours, 38 minutes of daylight; the longest day is June 21, with 15 hours, 46 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 5:01 AM on June 15, and the latest sunrise is 2 hours, 35 minutes later at 7:37 AM on November 3. The earliest sunset is at 4:07 PM on December 10, and the latest sunset is 4 hours, 41 minutes later at 8:48 PM on June 26.
Daylight saving time (DST) is observed in Walla Walla during 2018, starting in the spring on March 11, lasting 7.8 months, and ending in the fall on November 4.
Sunrise & Sunset with Twilight and Daylight Saving Time
The perceived humidity level in Walla Walla, as measured by the percentage of time in which the humidity comfort level is muggy, oppressive, or miserable, does not vary significantly over the course of the year, remaining a virtually constant 0% throughout.
Humidity Comfort Levels
The average hourly wind speed in Walla Walla experiences mild seasonal variation over the course of the year.
The windier part of the year lasts for 5.5 months, from October 30 to April 15, with average wind speeds of more than 7.5 miles per hour. The windiest day of the year is November 19, with an average hourly wind speed of 8.3 miles per hour.
The calmer time of year lasts for 6.5 months, from April 15 to October 30. The calmest day of the year is September 8, with an average hourly wind speed of 6.6 miles per hour.
Average Wind Speed
The predominant average hourly wind direction in Walla Walla varies throughout the year.
The wind is most often from the west for 6.6 months, from March 18 to October 6, with a peak percentage of 60% on June 30. The wind is most often from the south for 5.4 months, from October 6 to March 18, with a peak percentage of 64% on January 1.
Best Time of Year to Visit
To characterize how pleasant the weather is in Walla Walla throughout the year, we compute two travel scores.
The tourism score favors clear, rainless days with perceived temperatures between 65°F and 80°F. Based on this score, the best time of year to visit Walla Walla for general outdoor tourist activities is from early July to early September, with a peak score in the first week of August.
The beach/pool score favors clear, rainless days with perceived temperatures between 75°F and 90°F. Based on this score, the best time of year to visit Walla Walla for hot-weather activities is from mid July to mid August, with a peak score in the first week of August.
For each hour between 8:00 AM and 9:00 PM of each day in the analysis period (1980 to 2016), independent scores are computed for perceived temperature, cloud cover, and total precipitation. Those scores are combined into a single hourly composite score, which is then aggregated into days, averaged over all the years in the analysis period, and smoothed.
Our cloud cover score is 10 for fully clear skies, falling linearly to 9 for mostly clear skies, and to 1 for fully overcast skies.
Our precipitation score, which is based on the three-hour precipitation centered on the hour in question, is 10 for no precipitation, falling linearly to 9 for trace precipitation, and to 0 for 0.04 inches of precipitation or more.
Our tourism temperature score is 0 for perceived temperatures below 50°F, rising linearly to 9 for 65°F, to 10 for 75°F, falling linearly to 9 for 80°F, and to 1 for 90°F or hotter.
Our beach/pool temperature score is 0 for perceived temperatures below 65°F, rising linearly to 9 for 75°F, to 10 for 82°F, falling linearly to 9 for 90°F, and to 1 for 100°F or hotter.
The growing season in Walla Walla typically lasts for 7.7 months (235 days), from around March 14 to around November 4, rarely starting before February 15 or after April 8, and rarely ending before October 13 or after November 26.
Time Spent in Various Temperature Bands and the Growing Season
Based on growing degree days alone, the first spring blooms in Walla Walla should appear around March 28, only rarely appearing before March 12 or after April 14.
Growing Degree Days
The average daily incident shortwave solar energy experiences extreme seasonal variation over the course of the year.
The brighter period of the year lasts for 3.0 months, from May 20 to August 22, with an average daily incident shortwave energy per square meter above 6.4 kWh. The brightest day of the year is July 13, with an average of 7.7 kWh.
The darker period of the year lasts for 3.8 months, from October 27 to February 19, with an average daily incident shortwave energy per square meter below 2.5 kWh. The darkest day of the year is December 23, with an average of 1.2 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of Walla Walla are 46.065 deg latitude, -118.343 deg longitude, and 942 ft elevation.
The topography within 2 miles of Walla Walla contains only modest variations in elevation, with a maximum elevation change of 249 feet and an average elevation above sea level of 942 feet. Within 10 miles contains only modest variations in elevation (3,264 feet). Within 50 miles contains large variations in elevation (6,115 feet).
The area within 2 miles of Walla Walla is covered by artificial surfaces (69%) and cropland (25%), within 10 miles by cropland (78%) and grassland (10%), and within 50 miles by shrubs (39%) and cropland (30%).
This report illustrates the typical weather in Walla Walla, based on a statistical analysis of historical hourly weather reports and model reconstructions from January 1, 1980 to December 31, 2016.
Temperature and Dew Point
There are 4 weather stations near enough to contribute to our estimation of the temperature and dew point in Walla Walla.
For each station, the records are corrected for the elevation difference between that station and Walla Walla according to the International Standard Atmosphere , and by the relative change present in the MERRA-2 satellite-era reanalysis between the two locations.
The estimated value at Walla Walla is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Walla Walla and a given station.
The stations contributing to this reconstruction are: Walla Walla Regional Airport (89%, 5.5 kilometers, northeast); Eastern Oregon Regional Airport (5%, 57 kilometers, southwest); Meacham, Meacham (2.1%, 62 kilometers, south); and Tri-Cities Airport (4.3%, 64 kilometers, west).
Time zones for aiports and weather stations are provided by AskGeo.com .