Average Weather in Janesville California, United States
In Janesville, the summers are warm, arid, and mostly clear and the winters are chilly, wet, and partly cloudy. Over the course of the year, the temperature typically varies from 25°F to 87°F and is rarely below 14°F or above 94°F.
The hot season lasts for 3.1 months, from June 14 to September 18, with an average daily high temperature above 78°F. The hottest day of the year is July 29, with an average high of 87°F and low of 56°F.
The cold season lasts for 3.5 months, from November 17 to March 1, with an average daily high temperature below 50°F. The coldest day of the year is December 31, with an average low of 25°F and high of 41°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 Janesville, 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 Janesville begins around June 1 and lasts for 4.5 months, ending around October 18. On July 28, the clearest day of the year, the sky is clear, mostly clear, or partly cloudy 89% of the time, and overcast or mostly cloudy 11% of the time.
The cloudier part of the year begins around October 18 and lasts for 7.4 months, ending around June 1. On January 10, the cloudiest day of the year, the sky is overcast or mostly cloudy 57% of the time, and clear, mostly clear, or partly cloudy 43% 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 Janesville varies throughout the year.
The wetter season lasts 5.5 months, from October 31 to April 16, with a greater than 17% chance of a given day being a wet day. The chance of a wet day peaks at 32% on February 28.
The drier season lasts 6.5 months, from April 16 to October 31. The smallest chance of a wet day is 2% on July 19.
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 throughout the year is rain alone, with a peak probability of 26% on February 28.
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. Janesville experiences significant seasonal variation in monthly rainfall.
The rainy period of the year lasts for 8.8 months, from September 19 to June 13, with a sliding 31-day rainfall of at least 0.5 inches. The most rain falls during the 31 days centered around February 18, with an average total accumulation of 3.3 inches.
The rainless period of the year lasts for 3.2 months, from June 13 to September 19. The least rain falls around August 8, with an average total accumulation of 0.1 inches.
Average Monthly Rainfall
We report snowfall in liquid-equivalent terms. The actual depth of new snowfall is typically between 5 and 10 times the liquid-equivalent amount, assuming the ground is frozen. Colder, drier snow tends to be on the higher end of that range and warmer, wetter snow on the lower end.
As with rainfall, we consider the snowfall accumulated over a sliding 31-day period centered around each day of the year. Janesville experiences some seasonal variation in monthly liquid-equivalent snowfall.
The snowy period of the year lasts for 4.2 months, from November 16 to March 22, with a sliding 31-day liquid-equivalent snowfall of at least 0.1 inches. The most snow falls during the 31 days centered around January 3, with an average total liquid-equivalent accumulation of 0.5 inches.
The snowless period of the year lasts for 7.8 months, from March 22 to November 16. The least snow falls around July 18, with an average total liquid-equivalent accumulation of 0.0 inches.
Average Liquid-Equivalent Monthly Snowfall
The length of the day in Janesville varies significantly over the course of the year. In 2017, the shortest day is December 21, with 9 hours, 18 minutes of daylight; the longest day is June 21, with 15 hours, 3 minutes of daylight.
Hours of Daylight and Twilight
The earliest sunrise is at 5:31 AM on June 14, and the latest sunrise is 2 hours, 4 minutes later at 7:35 AM on November 4. The earliest sunset is at 4:35 PM on December 7, and the latest sunset is 4 hours, 0 minutes later at 8:36 PM on June 27.
Daylight saving time (DST) is observed in Janesville during 2017, starting in the spring on March 12, lasting 7.8 months, and ending in the fall on November 5.
Sunrise & Sunset with Twilight and Daylight Saving Time
The perceived humidity level in Janesville, 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
Average Wind Speed
The predominant average hourly wind direction in Janesville varies throughout the year.
The wind is most often from the south for 1.3 months, from February 5 to March 13 and for 1.7 weeks, from November 19 to December 1, with a peak percentage of 36% on February 23. The wind is most often from the west for 6.5 months, from March 13 to September 28, with a peak percentage of 59% on July 23. The wind is most often from the east for 1.7 months, from September 28 to November 19 and for 2.1 months, from December 1 to February 5, with a peak percentage of 35% on October 20.
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 3.4 months, from May 10 to August 23, with an average daily incident shortwave energy per square meter above 7.3 kWh. The brightest day of the year is July 1, with an average of 8.6 kWh.
The darker period of the year lasts for 3.5 months, from October 31 to February 15, with an average daily incident shortwave energy per square meter below 3.4 kWh. The darkest day of the year is December 19, with an average of 2.1 kWh.
Average Daily Incident Shortwave Solar Energy
For the purposes of this report, the geographical coordinates of Janesville are 40.297 deg latitude, -120.524 deg longitude, and 4,344 ft elevation.
The topography within 2 miles of Janesville contains very significant variations in elevation, with a maximum elevation change of 1,542 feet and an average elevation above sea level of 4,389 feet. Within 10 miles contains very significant variations in elevation (3,770 feet). Within 50 miles also contains extreme variations in elevation (6,949 feet).
The area within 2 miles of Janesville is covered by shrubs (61%), grassland (24%), and trees (12%), within 10 miles by shrubs (39%) and trees (34%), and within 50 miles by shrubs (52%) and trees (40%).
This report illustrates the typical weather in Janesville, 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 7 weather stations near enough to contribute to our estimation of the temperature and dew point in Janesville.
For each station, the records are corrected for the elevation difference between that station and Janesville 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 Janesville is computed as the weighted average of the individual contributions from each station, with weights proportional to the inverse of the distance between Janesville and a given station.
The stations contributing to this reconstruction are: Reno/Tahoe International Airport (20%, 111 kilometers, southeast); Truckee Tahoe Airport (17%, 114 kilometers, south); Blue Canyon-Nyack Airport (18%, 115 kilometers, south); Chico Municipal Airport (10%, 126 kilometers, southwest); Oroville Municipal Airport (10%, 130 kilometers, southwest); Alturas Municipal Airport (15%, 133 kilometers, north); and Redding Municipal Airport (9%, 152 kilometers, west).
Time zones for aiports and weather stations are provided by AskGeo.com .