Average Weather in Umatilla Oregon, United States
In Umatilla, the summers are hot and mostly clear, the winters are very cold and partly cloudy, and it is dry year round. Over the course of the year, the temperature typically varies from 27°F to 93°F and is rarely below 13°F or above 102°F.
Based on the tourism score, the best time of year to visit Umatilla for warm-weather activities is from late June to late August.
The hot season lasts for 3.0 months, from June 13 to September 11, with an average daily high temperature above 82°F. The hottest day of the year is July 30, with an average high of 93°F and low of 61°F.
The cold season lasts for 3.1 months, from November 16 to February 18, with an average daily high temperature below 50°F. The coldest day of the year is December 30, with an average low of 27°F and high of 39°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 Umatilla, 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 Umatilla begins around June 9 and lasts for 4.0 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 8.0 months, ending around June 9. On January 16, the cloudiest day of the year, the sky is overcast or mostly cloudy 65% of the time, and clear, mostly clear, or partly cloudy 35% 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 Umatilla varies throughout the year.
The wetter season lasts 7.6 months, from October 17 to June 4, with a greater than 13% chance of a given day being a wet day. The chance of a wet day peaks at 23% on November 29.
The drier season lasts 4.4 months, from June 4 to October 17. The smallest chance of a wet day is 3% on August 2.
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 20% on November 10.
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. Umatilla experiences some seasonal variation in monthly rainfall.
The rainy period of the year lasts for 8.3 months, from October 9 to June 17, with a sliding 31-day rainfall of at least 0.5 inches. The most rain falls during the 31 days centered around November 17, with an average total accumulation of 0.9 inches.
The rainless period of the year lasts for 3.7 months, from June 17 to October 9. The least rain falls around July 27, with an average total accumulation of 0.2 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. Umatilla experiences some seasonal variation in monthly liquid-equivalent snowfall.
The snowy period of the year lasts for 2.9 months, from November 20 to February 16, 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 31, with an average total liquid-equivalent accumulation of 0.3 inches.
The snowless period of the year lasts for 9.1 months, from February 16 to November 20. The least snow falls around July 22, with an average total liquid-equivalent accumulation of 0.0 inches.
Average Liquid-Equivalent Monthly Snowfall
The length of the day in Umatilla varies significantly over the course of the year. In 2018, the shortest day is December 21, with 8 hours, 39 minutes of daylight; the longest day is June 21, with 15 hours, 45 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 5:06 AM on June 15, and the latest sunrise is 2 hours, 34 minutes later at 7:40 AM on November 3. The earliest sunset is at 4:12 PM on December 10, and the latest sunset is 4 hours, 40 minutes later at 8:51 PM on June 26.
Daylight saving time (DST) is observed in Umatilla 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 Umatilla, 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 Umatilla experiences mild seasonal variation over the course of the year.
The windier part of the year lasts for 5.3 months, from February 25 to August 3, with average wind speeds of more than 8.2 miles per hour. The windiest day of the year is June 8, with an average hourly wind speed of 9.0 miles per hour.
The calmer time of year lasts for 6.8 months, from August 3 to February 25. The calmest day of the year is October 6, with an average hourly wind speed of 7.4 miles per hour.
Average Wind Speed
The predominant average hourly wind direction in Umatilla varies throughout the year.
The wind is most often from the west for 10 months, from January 16 to November 23, with a peak percentage of 79% on July 18. The wind is most often from the south for 3.3 weeks, from November 23 to December 16, with a peak percentage of 34% on November 27. The wind is most often from the north for 1.0 months, from December 16 to January 16, with a peak percentage of 33% on January 1.
Best Time of Year to Visit
To characterize how pleasant the weather is in Umatilla 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 Umatilla for general outdoor tourist activities is from late June to late August, with a peak score in the last week of July.
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 Umatilla for hot-weather activities is from mid July to mid August, with a peak score in the last week of July.
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 Umatilla typically lasts for 5.9 months (179 days), from around April 18 to around October 14, rarely starting before March 29 or after May 9, and rarely ending before September 26 or after November 1.
Time Spent in Various Temperature Bands and the Growing Season
Based on growing degree days alone, the first spring blooms in Umatilla should appear around March 29, only rarely appearing before March 18 or after April 11.
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 3.2 months, from May 14 to August 22, with an average daily incident shortwave energy per square meter above 6.5 kWh. The brightest day of the year is July 13, with an average of 7.8 kWh.
The darker period of the year lasts for 3.7 months, from October 28 to February 18, with an average daily incident shortwave energy per square meter below 2.6 kWh. The darkest day of the year is December 26, with an average of 1.2 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of Umatilla are 45.917 deg latitude, -119.343 deg longitude, and 430 ft elevation.
The topography within 2 miles of Umatilla contains only modest variations in elevation, with a maximum elevation change of 381 feet and an average elevation above sea level of 362 feet. Within 10 miles contains only modest variations in elevation (1,260 feet). Within 50 miles contains very significant variations in elevation (5,659 feet).
The area within 2 miles of Umatilla is covered by shrubs (32%), cropland (24%), water (22%), and artificial surfaces (21%), within 10 miles by cropland (55%) and shrubs (30%), and within 50 miles by shrubs (51%) and cropland (34%).
This report illustrates the typical weather in Umatilla, 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 3 weather stations near enough to contribute to our estimation of the temperature and dew point in Umatilla.
For each station, the records are corrected for the elevation difference between that station and Umatilla 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 Umatilla is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Umatilla and a given station.
The stations contributing to this reconstruction are: Hermiston Municipal Airport (83%, 12 kilometers, southeast); Tri-Cities Airport (15%, 43 kilometers, northeast); and The Dalles Municipal Airport (2.4%, 145 kilometers, west).
Time zones for aiports and weather stations are provided by AskGeo.com .