This report describes the typical weather at the Janesville (Janesville, Wisconsin, United States) weather station over the course of an average year. It is based on the historical records from 2011 to 2014. Earlier records are either unavailable or unreliable.
Janesville, Wisconsin has a humid continental climate with hot summers and no dry season. The area within 25 mi of this station is covered by grasslands (58%), croplands (36%), built-up areas (3%), and lakes and rivers (2%).
Over the course of a year, the temperature typically varies from 13Â°F to 82Â°F and is rarely below 4Â°F or above 87Â°F.
The warm season lasts from June 4 to September 11 with an average daily high temperature above 71Â°F. The hottest day of the year is July 14, with an average high of 82Â°F and low of 67Â°F.
The cold season lasts from November 30 to March 5 with an average daily high temperature below 38Â°F. The coldest day of the year is January 12, with an average low of 13Â°F and high of 28Â°F.
The length of the day varies significantly over the course of the year. The shortest day is December 21 with 9:03 hours of daylight; the longest day is June 21 with 15:20 hours of daylight.
The earliest sunrise is at 5:17am on June 18 and the latest sunset is at 8:39pm on June 24. The latest sunrise is at 7:30am on November 1 and the earliest sunset is at 4:22pm on December 11.
Daylight saving time (DST) is observed in this location during 2014, starting in the spring on March 9 and ending in the fall on November 2.
The median cloud cover ranges from 25% (mostly clear) to 66% (partly cloudy). The sky is cloudiest on February 9 and clearest on September 10. The clearer part of the year begins around May 18. The cloudier part of the year begins around November 4.
On September 10, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 74% of the time, and overcast or mostly cloudy 25% of the time.
On February 9, the cloudiest day of the year, the sky is overcast, mostly cloudy, or partly cloudy 63% 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 January 12, occurring in 49% of days. Precipitation is least likely around September 8, occurring in 23% of days.
Over the entire year, the most common forms of precipitation are light snow, light rain, thunderstorms, and moderate rain.
Light snow is the most severe precipitation observed during 30% of those days with precipitation. It is most likely around January 31, when it is observed during 36% of all days.
Light rain is the most severe precipitation observed during 25% of those days with precipitation. It is most likely around May 12, when it is observed during 18% of all days.
Thunderstorms are the most severe precipitation observed during 15% of those days with precipitation. They are most likely around June 24, when it is observed during 13% of all days.
Moderate rain is the most severe precipitation observed during 15% of those days with precipitation. It is most likely around May 23, when it is observed during 10% of all days.
During the warm season, which lasts from June 4 to September 11, there is a 29% 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 (36% of days with precipitation have at worst thunderstorms), light rain (33%), moderate rain (16%), and heavy rain (8%).
During the cold season, which lasts from November 30 to March 5, there is a 44% 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 (66% of days with precipitation have at worst light snow), moderate snow (14%), moderate rain (7%), and light rain (6%).
The likelihood of snow falling is highest around January 30, occurring in 43% of days. The season in which it is relatively likely for snow to fall spans from November 19 to March 30.
Either snow rarely accumulates at this location or snow depth measurements are unavailable or unreliable.
The relative humidity typically ranges from 44% (comfortable) to 90% (very humid) over the course of the year, rarely dropping below 30% (comfortable), or exceeding 93% (very humid).
The air is driest around May 14, at which time the relative humidity drops below 52% (mildly humid) three days out of four; it is most humid around September 24, exceeding 89% (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 6Â°F (dry) to 67Â°F (muggy) and is rarely below -4Â°F (dry) or above 71Â°F (very muggy).
There are two periods in the year that are most comfortable: The first is between May 18 and July 12 and the second is between July 30 and September 22. 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 20 mph (calm to fresh breeze), rarely exceeding 35 mph (high wind).
The highest average wind speed of 11 mph (gentle breeze) occurs around April 12, at which time the average daily maximum wind speed is 19 mph (fresh breeze).
The lowest average wind speed of 5 mph (light breeze) occurs around August 9, at which time the average daily maximum wind speed is 11 mph (gentle breeze).