Summer Weather in San Luis Colorado, United States

Daily high temperatures are around 74°F, rarely falling below 60°F or exceeding 84°F. The highest daily average high temperature is 78°F on July 8.

Daily low temperatures increase by 5°F, from 40°F to 45°F, rarely falling below 33°F or exceeding 54°F. The highest daily average low temperature is 50°F on July 23.

For reference, on July 8, the hottest day of the year, temperatures in San Luis typically range from 48°F to 78°F, while on January 7, the coldest day of the year, they range from 10°F to 34°F.

The figure below shows you a compact characterization of the hourly average summer temperatures. The horizontal axis is the day, the vertical axis is the hour of the day, and the color is the average temperature for that hour and day.

Koprivshtitsa, Bulgaria (6,088 miles away); Norashen, Armenia (6,701 miles); and Xining, China (7,055 miles) are the far-away foreign places with temperatures most similar to San Luis (view comparison).

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The summer in San Luis experiences essentially constant cloud cover, with the percentage of time that the sky is overcast or mostly cloudy remaining about 30% throughout the season. The highest chance of overcast or mostly cloudy conditions is 36% on August 8.

The clearest day of the summer is June 22, with clear, mostly clear, or partly cloudy conditions 77% of the time.

For reference, on February 10, the cloudiest day of the year, the chance of overcast or mostly cloudy conditions is 38%, while on September 29, the clearest day of the year, the chance of clear, mostly clear, or partly cloudy skies is 79%.

A wet day is one with at least 0.04 inches of liquid or liquid-equivalent precipitation. In San Luis, the chance of a wet day over the course of the summer is very rapidly increasing, starting the season at 16% and ending it at 26%.

For reference, the year's highest daily chance of a wet day is 36% on August 10, and its lowest chance is 8% on January 14.

Rainfall

To show variation within the season and not just the monthly totals, we show the rainfall accumulated over a sliding 31-day period centered around each day.

The average sliding 31-day rainfall during the summer in San Luis is gradually increasing, starting the season at 0.8 inches, when it rarely exceeds 1.7 inches or falls below 0.1 inches, and ending the season at 1.2 inches, when it rarely exceeds 2.2 inches or falls below 0.4 inches.

The highest average 31-day accumulation is 1.6 inches on August 3. The lowest average 31-day accumulation is 0.7 inches on June 14.

Over the course of the summer in San Luis, the length of the day is rapidly decreasing. From the start to the end of the season, the length of the day decreases by 1 hour, 34 minutes, implying an average daily decrease of 1 minute, 2 seconds, and weekly decrease of 7 minutes, 15 seconds.

The shortest day of the summer is August 31, with 12 hours, 59 minutes of daylight and the longest day is June 20, with 14 hours, 44 minutes of daylight.

The earliest sunrise of the summer in San Luis is 5:40 AM on June 13 and the latest sunrise is 51 minutes later at 6:31 AM on August 31.

The latest sunset is 8:26 PM on June 27 and the earliest sunset is 55 minutes earlier at 7:31 PM on August 31.

Daylight saving time is observed in San Luis during 2025, but it neither starts nor ends during the summer, so the entire season is in daylight saving time.

For reference, on June 21, the longest day of the year, the Sun rises at 5:41 AM and sets 14 hours, 44 minutes later, at 8:25 PM, while on December 21, the shortest day of the year, it rises at 7:12 AM and sets 9 hours, 36 minutes later, at 4:48 PM.

The figure below presents a compact representation of the sun's elevation (the angle of the sun above the horizon) and azimuth (its compass bearing) for every hour of every day in the reporting period. The horizontal axis is the day of the year and the vertical axis is the hour of the day. For a given day and hour of that day, the background color indicates the azimuth of the sun at that moment. The black isolines are contours of constant solar elevation.

The figure below presents a compact representation of key lunar data for the summer of 2025. The horizontal axis is the day, the vertical axis is the hour of the day, and the colored areas indicate when the moon is above the horizon. The vertical gray bars (new Moons) and blue bars (full Moons) indicate key Moon phases. The label associated with each bar indicates the date and time that the phase is obtained, and the companion time labels indicate the rise and set times of the Moon for the nearest time interval in which the moon is above the horizon.

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 chance that a given day will be muggy in San Luis is essentially constant during the summer, remaining around 0% throughout.

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 San Luis is rapidly decreasing during the summer, decreasing from 8.3 miles per hour to 6.1 miles per hour over the course of the season.

For reference, on April 11, the windiest day of the year, the daily average wind speed is 9.8 miles per hour, while on August 2, the calmest day of the year, the daily average wind speed is 5.5 miles per hour.

The lowest daily average wind speed during the summer is 5.5 miles per hour on August 3.

The hourly average wind direction in San Luis throughout the summer is predominantly from the west, with a peak proportion of 60% on June 7.

Definitions of the growing season vary throughout the world, but for the purposes of this report, we define it as the longest continuous period of non-freezing temperatures (≥ 32°F) in the year (the calendar year in the Northern Hemisphere, or from July 1 until June 30 in the Southern Hemisphere).

The growing season in San Luis typically lasts for 4.0 months (122 days), from around May 25 to around September 24, rarely starting before May 5 or after June 15, and rarely ending before September 7 or after October 12.

The summer in San Luis is more likely than not fully within the growing season, with the chance that a given day is in the growing season reaching a high of 100% on July 29.

Growing degree days are a measure of yearly heat accumulation used to predict plant and animal development, and defined as the integral of warmth above a base temperature, discarding any excess above a maximum temperature. In this report, we use a base of 50°F and a cap of 86°F.

The average accumulated growing degree days in San Luis are very rapidly increasing during the summer, increasing by 1,065°F, from 241°F to 1,306°F, over the course of the season.

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 in San Luis is rapidly decreasing during the summer, falling by 1.8 kWh, from 8.1 kWh to 6.3 kWh, over the course of the season.

The highest average daily incident shortwave solar energy during the summer is 8.3 kWh on June 12.

For the purposes of this report, the geographical coordinates of San Luis are 37.201 deg latitude, -105.424 deg longitude, and 7,976 ft elevation.

The topography within 2 miles of San Luis contains significant variations in elevation, with a maximum elevation change of 581 feet and an average elevation above sea level of 8,059 feet. Within 10 miles contains significant variations in elevation (4,167 feet). Within 50 miles also contains extreme variations in elevation (8,264 feet).

The area within 2 miles of San Luis is covered by shrubs (69%) and cropland (19%), within 10 miles by shrubs (64%) and trees (24%), and within 50 miles by shrubs (46%) and trees (38%).