Average Weather in Shelby Montana, United States
In Shelby, the summers are short and warm; the winters are freezing, dry, and windy; and it is partly cloudy year round. Over the course of the year, the temperature typically varies from 13°F to 83°F and is rarely below -13°F or above 93°F.
Based on the tourism score, the best time of year to visit Shelby for warm-weather activities is from early July to mid August.
The warm season lasts for 2.8 months, from June 16 to September 11, with an average daily high temperature above 73°F. The hottest day of the year is July 31, with an average high of 83°F and low of 54°F.
The cold season lasts for 3.6 months, from November 18 to March 4, with an average daily high temperature below 41°F. The coldest day of the year is January 1, with an average low of 13°F and high of 31°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 Shelby, 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 Shelby begins around June 18 and lasts for 3.6 months, ending around October 5. On July 23, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 75% of the time, and overcast or mostly cloudy 25% of the time.
The cloudier part of the year begins around October 5 and lasts for 8.4 months, ending around June 18. On March 17, the cloudiest day of the year, the sky is overcast or mostly cloudy 62% of the time, and clear, mostly clear, or partly cloudy 38% of the time.
Cloud Cover Categories
0% clear 20% mostly clear 40% partly cloudy 60% mostly cloudy 80% overcast 100%
A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. The chance of wet days in Shelby varies throughout the year.
The wetter season lasts 2.2 months, from May 7 to July 14, with a greater than 16% chance of a given day being a wet day. The chance of a wet day peaks at 29% on June 4.
The drier season lasts 9.8 months, from July 14 to May 7. The smallest chance of a wet day is 3% on January 31.
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 in Shelby changes throughout the year.
Rain alone is the most common for 7.7 months, from March 20 to November 8. The highest chance of a day with rain alone is 29% on June 4.
Snow alone is the most common for 4.3 months, from November 8 to March 20. The highest chance of a day with snow alone is 4% on March 9.
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. Shelby experiences significant seasonal variation in monthly rainfall.
The rainy period of the year lasts for 6.1 months, from April 9 to October 11, with a sliding 31-day rainfall of at least 0.5 inches. The most rain falls during the 31 days centered around June 7, with an average total accumulation of 2.3 inches.
The rainless period of the year lasts for 5.9 months, from October 11 to April 9. The least rain falls around February 4, with an average total accumulation of 0.0 inches.
Average Monthly Rainfall
The sliding 31-day liquid-equivalent quantity of snowfall in Shelby does not vary significantly over the course of the year, staying within 0.1 inches of 0.1 inches throughout.
Average Liquid-Equivalent Monthly Snowfall
The length of the day in Shelby varies extremely over the course of the year. In 2018, the shortest day is December 21, with 8 hours, 18 minutes of daylight; the longest day is June 21, with 16 hours, 8 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 5:24 AM on June 16, and the latest sunrise is 2 hours, 54 minutes later at 8:19 AM on December 31. The earliest sunset is at 4:31 PM on December 10, and the latest sunset is 5 hours, 1 minute later at 9:33 PM on June 25.
Daylight saving time (DST) is observed in Shelby 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 Shelby, 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
dry 55°F comfortable 60°F humid 65°F muggy 70°F oppressive 75°F miserable
The average hourly wind speed in Shelby experiences significant seasonal variation over the course of the year.
The windier part of the year lasts for 7.7 months, from October 5 to May 29, with average wind speeds of more than 10.3 miles per hour. The windiest day of the year is January 18, with an average hourly wind speed of 12.1 miles per hour.
The calmer time of year lasts for 4.3 months, from May 29 to October 5. The calmest day of the year is August 4, with an average hourly wind speed of 8.5 miles per hour.
Average Wind Speed
The predominant average hourly wind direction in Shelby is from the west throughout the year.
Best Time of Year to Visit
To characterize how pleasant the weather is in Shelby 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 Shelby for general outdoor tourist activities is from early July to mid 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 Shelby 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 Shelby typically lasts for 4.4 months (135 days), from around May 12 to around September 24, rarely starting before April 26 or after May 28, and rarely ending before September 6 or after October 13.
Time Spent in Various Temperature Bands and the Growing Season
Based on growing degree days alone, the first spring blooms in Shelby should appear around April 29, only rarely appearing before April 17 or after May 13.
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 3.3 months, from May 10 to August 19, with an average daily incident shortwave energy per square meter above 6.2 kWh. The brightest day of the year is July 8, with an average of 7.5 kWh.
The darker period of the year lasts for 3.6 months, from October 27 to February 15, with an average daily incident shortwave energy per square meter below 2.4 kWh. The darkest day of the year is December 24, with an average of 1.2 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of Shelby are 48.505 deg latitude, -111.857 deg longitude, and 3,419 ft elevation.
The topography within 2 miles of Shelby contains only modest variations in elevation, with a maximum elevation change of 272 feet and an average elevation above sea level of 3,373 feet. Within 10 miles contains only modest variations in elevation (787 feet). Within 50 miles contains significant variations in elevation (4,245 feet).
The area within 2 miles of Shelby is covered by grassland (83%) and cropland (12%), within 10 miles by grassland (68%) and cropland (30%), and within 50 miles by grassland (52%) and cropland (46%).
This report illustrates the typical weather in Shelby, 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 Shelby.
For each station, the records are corrected for the elevation difference between that station and Shelby 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 Shelby is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Shelby and a given station.
The stations contributing to this reconstruction are: Cut Bank Municipal Airport (45%, 40 kilometers, west); Milk River (20%, 71 kilometers, north); Masinasin AGDM (20%, 72 kilometers, north); and Julie (15%, 87 kilometers, south).
Time zones for aiports and weather stations are provided by AskGeo.com .