Average Weather in Walla Walla Washington, United States
In Walla Walla, the temperature typically varies from 30°F to 93°F over the course of the year, and is rarely below 17°F or above 102°F.
The hot season lasts for 84 days, from June 19 to September 11, 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 100 days, from November 14 to February 22, with an average daily high temperature below 51°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
The length of the day in Walla Walla varies significantly over the course of the year. In 2017, 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, 37 minutes later at 7:38 AM on November 4. 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 25.
Daylight saving time (DST) is observed in Walla Walla during 2017, starting in the spring on March 12, lasting 237 days, and ending in the fall on November 5.
Sunrise & Sunset with Twilight and Daylight Saving Time
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 119 days, 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 246 days, 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.
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 222 days, from October 22 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 143 days, from June 1 to October 22. 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 in the year. Walla Walla experiences some seasonal variation in monthly rainfall.
The rainy period of the year lasts for 308 days, from September 3 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 57 days, from July 8 to September 3. The least rain falls around July 30, with and 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 in the year. Walla Walla experiences some seasonal variation in monthly liquid-equivalent snowfall.
The snowy period of the year lasts for 87 days, from November 23 to February 18, 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 278 days, from February 18 to November 23. The least snow falls around July 14, with an average total liquid-equivalent accumulation of 0.0 inches.
Average Liquid-Equivalent Monthly Snowfall
We base the humidity comfort level on the dew point, as it determines whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid. Unlike temperature, which typically varies significantly between night and day, dew point tends to change more slowly, so while the temperature may drop at night, a muggy day is typically followed by a muggy night.
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
This section discusses the wide-area hourly average wind vector (speed and direction) at 10 meters above the ground. The wind experienced at any given location is highly dependent on local topography and other factors, and instantaneous wind speed and direction vary more widely than hourly averages.The average hourly wind speed in Walla Walla does not vary significantly over the course of the year, remaining within 0.4 miles per hour of 4.0 miles per hour throughout.
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 202 days, from March 18 to October 6, with a peak percentage of 61% on June 23. The wind is most often from the south for 163 days, from October 6 to March 18, with a peak percentage of 66% on December 26.
This section discusses the total daily incident shortwave solar energy reaching the surface of the ground over a wide area, taking full account of seasonal variations in the length of the day, the elevation of the Sun above the horizon, and absorption by clouds and other atmospheric constituents. Shortwave radiation includes visible light and ultraviolet radiation.
The average daily incident shortwave solar energy experiences very significant seasonal variation over the course of the year.
The brighter period of the year lasts for 95 days, from May 20 to August 23, with an average daily incident shortwave energy per square meter above 6.3 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 117 days, from October 26 to February 20, 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 (map ).
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 large variations in elevation (3,264 feet). Within 50 miles contains extreme 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).
All data relating to the Sun's position (e.g., sunrise and sunset) are computed using astronomical formulas from the book, Astronomical Tables of the Sun, Moon and Planets , by Jean Meeus.
All other weather data, including cloud cover, precipitation, wind speed and direction, and solar flux, come from NASA's MERRA-2 Modern-Era Retrospective Analysis . This reanalysis combines a variety of wide-area measurements in a state-of-the-art global meteorological model to reconstruct the hourly history of weather throughout the world on a 50-kilometer grid.
Land Use data comes from the Global Land Cover SHARE database , published by the Food and Agriculture Organization of the United Nations.
Elevation data comes from the Shuttle Radar Topography Mission (SRTM) , published by NASA's Jet Propulsion Laboratory.
Names, locations, and time zones of places and some airports come from the GeoNames Geographical Database .
Time zones for aiports and weather stations are provided by AskGeo.com .