Climate Insights for Janesville

The climate in Janesville is cool. The average annual temperature is 8°C and approximately 1097mm of precipitation falls per year. Janesville receives a notable amount of rainfall throughout the year, including during its driest month. Janesville is in the Northern Hemisphere. Summer begins at the end of June and lasts through September. The summer months are: July, June, August. The coldest months are January, February, December, when temperatures can drop to -12°C. Snowfall occurs from January to December, with around 159cm accumulating over the season.

Janesville has a wide annual temperature range, spanning 40°C from the coldest to warmest months. The warmest month is July, when average highs reach 28°C and the mean temperature sits around 23°C. The coldest month is January, when overnight lows fall to -12°C and the daily average is -8°C. On average, daily temperatures fluctuate by about 9°C between overnight lows and afternoon highs. The sharpest temperature change occurs between September and October, with a 9°C shift in average temperatures.

Janesville is a moderately rainy area, receiving approximately 1097mm of precipitation annually, which averages out to around 91mm per month. The wettest month is September, averaging 160mm of rainfall. May and June also tend to see above-average precipitation. The driest month is January, with just 40mm. That's 120mm less than September, the wettest month. Precipitation varies noticeably between seasons, with the second half (July to December) of the year generally seeing more rainfall. Snowfall is a regular feature from January to December, with around 159cm accumulating over the season. February typically sees the most snow at around 35cm.

Janesville is relatively calm, with an average annual wind speed of 4km/h. For context, sustained winds below 12km/h are generally light, while anything above 25km/h is considered strong. The windiest month is October, averaging 5km/h, though still comfortable for most outdoor activities. The calmest conditions occur in August, with average winds dropping to 3km/h, making it an ideal period for wind-sensitive activities. There is moderate seasonal variation in wind speed, with a 2km/h gap between the calmest and windiest months.

It is currently spring in Janesville, which began on March 20, 2026. Janesville is in the Northern Hemisphere, where spring begins in March, summer in June, autumn in September, and winter in December. The warmest period peaks in July at around 28°C, while the coldest stretch bottoms out in January near -12°C. Summer is next, beginning on June 21, 2026 — 1 days from now.

The table below shows monthly climate averages for Janesville based on historical weather data. Min and max temperatures represent typical overnight lows and afternoon highs for each month, shown in degrees Celsius (°C). Precipitation is measured in millimetres (mm) and indicates the average total rainfall per month. Snow is measured in centimetres (cm) and reflects average monthly snowfall accumulation. Wind speed is the average sustained speed in kilometres per hour (km/h). All values are based on averages from over 10 years of historical weather data. The current month is highlighted for quick reference.