Climate and Average Weather Year Round in Blue Grass Iowa, United States

In Blue Grass, the summers are long, warm, humid, and wet; the winters are freezing, snowy, and windy; and it is partly cloudy year round. Over the course of the year, the temperature typically varies from 15°F to 85°F and is rarely below -4°F or above 93°F.

Based on the tourism score, the best time of year to visit Blue Grass for warm-weather activities is from mid June to mid September.

The warm season lasts for 4.0 months, from May 19 to September 21, with an average daily high temperature above 74°F. The hottest month of the year in Blue Grass is July, with an average high of 84°F and low of 65°F.

The cold season lasts for 3.1 months, from November 30 to March 1, with an average daily high temperature below 41°F. The coldest month of the year in Blue Grass is January, with an average low of 16°F and high of 31°F.

In Blue Grass, 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 Blue Grass begins around June 11 and lasts for 4.5 months, ending around October 26.

The clearest month of the year in Blue Grass is August, during which on average the sky is clear, mostly clear, or partly cloudy 68% of the time.

The cloudier part of the year begins around October 26 and lasts for 7.5 months, ending around June 11.

The cloudiest month of the year in Blue Grass is December, during which on average the sky is overcast or mostly cloudy 55% 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 Blue Grass varies throughout the year.

The wetter season lasts 5.6 months, from April 5 to September 24, with a greater than 26% chance of a given day being a wet day. The month with the most wet days in Blue Grass is June, with an average of 11.9 days with at least 0.04 inches of precipitation.

The drier season lasts 6.4 months, from September 24 to April 5. The month with the fewest wet days in Blue Grass is January, with an average of 3.9 days with at least 0.04 inches of precipitation.

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 Blue Grass changes throughout the year.

Rain alone is the most common for 11 months, from February 5 to December 22. The month with the most days of rain alone in Blue Grass is June, with an average of 11.9 days.

Snow alone is the most common for 1.5 months, from December 22 to February 5. The month with the most days of snow alone in Blue Grass is January, with an average of 1.8 days.

Rainfall

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. Blue Grass experiences significant seasonal variation in monthly rainfall.

Rain falls throughout the year in Blue Grass. The month with the most rain in Blue Grass is June, with an average rainfall of 4.2 inches.

The month with the least rain in Blue Grass is January, with an average rainfall of 0.4 inches.

Snowfall

As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day of the year. Blue Grass experiences significant seasonal variation in monthly snowfall.

The snowy period of the year lasts for 4.4 months, from November 15 to March 28, with a sliding 31-day snowfall of at least 1.0 inches. The month with the most snow in Blue Grass is January, with an average snowfall of 3.9 inches.

The snowless period of the year lasts for 7.6 months, from March 28 to November 15. The least snow falls around July 21, with an average total accumulation of 0.0 inches.

The length of the day in Blue Grass varies significantly over the course of the year. In 2026, the shortest day is December 21, with 9 hours, 10 minutes of daylight; the longest day is June 21, with 15 hours, 11 minutes of daylight.

The earliest sunrise is at 5:28 AM on June 14, and the latest sunrise is 2 hours, 5 minutes later at 7:33 AM on October 31. The earliest sunset is at 4:33 PM on December 8, and the latest sunset is 4 hours, 8 minutes later at 8:41 PM on June 27.

Daylight saving time (DST) is observed in Blue Grass during 2026, starting in the spring on March 8, lasting 7.8 months, and ending in the fall on November 1.

The figure below presents a compact representation of key lunar data for 2026. 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.

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.

Blue Grass experiences extreme seasonal variation in the perceived humidity.

The muggier period of the year lasts for 3.6 months, from May 31 to September 18, during which time the comfort level is muggy, oppressive, or miserable at least 13% of the time. The month with the most muggy days in Blue Grass is July, with 15.5 days that are muggy or worse.

The least muggy day of the year is February 16, when muggy conditions are essentially unheard of.

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 Blue Grass experiences significant seasonal variation over the course of the year.

The windier part of the year lasts for 7.5 months, from October 8 to May 25, with average wind speeds of more than 10.1 miles per hour. The windiest month of the year in Blue Grass is March, with an average hourly wind speed of 12.3 miles per hour.

The calmer time of year lasts for 4.5 months, from May 25 to October 8. The calmest month of the year in Blue Grass is August, with an average hourly wind speed of 7.9 miles per hour.

The predominant average hourly wind direction in Blue Grass varies throughout the year.

The wind is most often from the north for 1.9 months, from February 11 to April 7, with a peak percentage of 32% on February 19. The wind is most often from the south for 7.5 months, from April 7 to November 23, with a peak percentage of 39% on September 6. The wind is most often from the west for 2.6 months, from November 23 to February 11, with a peak percentage of 35% on January 1.

To characterize how pleasant the weather is in Blue Grass 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 Blue Grass for general outdoor tourist activities is from mid June to mid September, with a peak score in the last 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 Blue Grass for hot-weather activities is from late June to mid August, with a peak score in the third week of July.

Methodology

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.

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 Blue Grass typically lasts for 5.8 months (175 days), from around April 21 to around October 13, rarely starting before April 3 or after May 8, and rarely ending before September 24 or after October 31.

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.

Based on growing degree days alone, the first spring blooms in Blue Grass should appear around April 9, only rarely appearing before March 26 or after April 23.

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 extreme seasonal variation over the course of the year.

The brighter period of the year lasts for 3.6 months, from May 3 to August 24, with an average daily incident shortwave energy per square meter above 5.9 kWh. The brightest month of the year in Blue Grass is July, with an average of 6.8 kWh.

The darker period of the year lasts for 3.2 months, from November 2 to February 10, with an average daily incident shortwave energy per square meter below 2.8 kWh. The darkest month of the year in Blue Grass is December, with an average of 1.8 kWh.

For the purposes of this report, the geographical coordinates of Blue Grass are 41.509 deg latitude, -90.766 deg longitude, and 787 ft elevation.

The topography within 2 miles of Blue Grass contains only modest variations in elevation, with a maximum elevation change of 151 feet and an average elevation above sea level of 772 feet. Within 10 miles also contains only modest variations in elevation (269 feet). Within 50 miles contains only modest variations in elevation (614 feet).

The area within 2 miles of Blue Grass is covered by cropland (83%) and trees (12%), within 10 miles by cropland (72%) and trees (12%), and within 50 miles by cropland (88%).