This report describes the typical weather at the Mason City Municipal Airport (Mason City, Iowa, United States) weather station over the course of an average year. It is based on the historical records from 1974 to 2012. Earlier records are either unavailable or unreliable.
Mason City, Iowa has a humid continental climate with hot summers and no dry season. The area within 25 mi of this station is covered by croplands (99%).
Over the course of a year, the temperature typically varies from 6°F to 83°F and is rarely below -12°F or above 92°F.
The warm season lasts from May 19 to September 19 with an average daily high temperature above 71°F. The hottest day of the year is July 11, with an average high of 83°F and low of 63°F.
The cold season lasts from November 27 to March 3 with an average daily high temperature below 35°F. The coldest day of the year is January 17, with an average low of 6°F and high of 23°F.
The length of the day varies significantly over the course of the year. The shortest day is December 21 with 9:00 hours of daylight; the longest day is June 20 with 15:23 hours of daylight.
The earliest sunrise is at 5:32am on June 14 and the latest sunset is at 8:58pm on June 26. The latest sunrise is at 7:52am on November 3 and the earliest sunset is at 4:37pm on December 9.
Daylight savings time (DST) is observed in this location during 2012, starting in the spring on March 11 and ending in the fall on November 4.
The median cloud cover ranges from 40% (mostly clear) to 85% (mostly cloudy). The sky is cloudiest on December 13 and clearest on September 10. The clearer part of the year begins around May 21. The cloudier part of the year begins around October 30.
On September 10, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 61% of the time, and overcast or mostly cloudy 39% of the time.
On December 13, the cloudiest day of the year, the sky is overcast, mostly cloudy, or partly cloudy 64% of the time, and clear or mostly clear 36% of the time.
The probability that precipitation will be observed at this location varies throughout the year. Precipitation is most likely around December 26, occurring in 49% of days. Precipitation is least likely around September 28, occurring in 34% of days.
Over the entire year, the most common forms of precipitation are light snow, light rain, and thunderstorms.
Light snow is the most severe precipitation observed during 28% of those days with precipitation. It is most likely around January 15, when it is observed during 33% of all days.
Light rain is the most severe precipitation observed during 26% of those days with precipitation. It is most likely around May 13, when it is observed during 20% of all days.
Thunderstorms are the most severe precipitation observed during 25% of those days with precipitation. They are most likely around June 27, when it is observed during 25% of all days.
During the warm season, which lasts from May 19 to September 19, there is a 40% average chance that precipitation will be observed at some point during a given day. When precipitation does occur it is most often in the form of thunderstorms (54% of days with precipitation have at worst thunderstorms), light rain (31%), and moderate rain (9%).
During the cold season, which lasts from November 27 to March 3, there is a 47% average chance that precipitation will be observed at some point during a given day. When precipitation does occur it is most often in the form of light snow (62% of days with precipitation have at worst light snow), moderate snow (15%), light rain (8%), and drizzle (6%).
The likelihood of snow falling is highest around January 15, occurring in 43% of days. The season in which it is relatively likely for snow to fall spans from November 2 to April 8.
Either snow rarely accumulates at this location or snow depth measurements are unavailable or unreliable.
The relative humidity typically ranges from 43% (comfortable) to 96% (very humid) over the course of the year, rarely dropping below 22% (dry) and reaching as high as 100% (very humid).
The air is driest around May 4, at which time the relative humidity drops below 55% (mildly humid) three days out of four; it is most humid around August 14, exceeding 94% (very humid) three days out of four.
Dew point is often a better measure of how comfortable a person will find the weather than relative humidity because it more directly relates to whether perspiration will evaporate from the skin, thereby cooling the body. Lower dew points feel drier and higher dew points feel more humid.
Over the course of a year, the dew point typically varies from 1°F (dry) to 69°F (muggy) and is rarely below -21°F (dry) or above 76°F (very muggy).
There are two periods in the year that are most comfortable: The first is between May 12 and June 28 and the second is between August 28 and September 29. The air feels neither too dry nor too muggy during these periods.
Over the course of the year typical wind speeds vary from 0 mph to 22 mph (calm to fresh breeze), rarely exceeding 30 mph (strong breeze).
The highest average wind speed of 14 mph (moderate breeze) occurs around April 6, at which time the average daily maximum wind speed is 22 mph (fresh breeze).
The lowest average wind speed of 8 mph (gentle breeze) occurs around August 4, at which time the average daily maximum wind speed is 15 mph (moderate breeze).