Climate Insights for Janesville

The climate in Janesville is temperate. The average annual temperature is 11°C and approximately 540mm of precipitation falls per year. January is the wettest month, receiving around 107mm of rainfall. Janesville is in the Northern Hemisphere. Summer begins at the end of June and lasts through September. The summer months are: July, August, June. The coldest months are December, February, January, when temperatures can drop to -4°C. Janesville experiences heavy snowfall, typically from January through December.

Janesville has a wide annual temperature range, spanning 36°C from the coldest to warmest months. The warmest month is July, when average highs reach 32°C and the mean temperature sits around 24°C. The coldest month is December, when overnight lows fall to -4°C and the daily average is 0°C. On average, daily temperatures fluctuate by about 13°C between overnight lows and afternoon highs. The sharpest temperature change occurs between September and October, with a 7°C shift in average temperatures.

Janesville is a relatively dry area, receiving approximately 540mm of precipitation annually, which averages out to around 45mm per month. The wettest month is January, averaging 107mm of rainfall. March and February also tend to see above-average precipitation. The driest month is July, with just 6mm. That's 101mm less than January, the wettest month. Rainfall is heavily concentrated in certain months, creating a distinct wet and dry season. Visitors should plan around these patterns, as the difference between peak and low months is dramatic. Janesville receives heavy snowfall, accumulating around 218cm annually from January through December. The snowiest month is January, with approximately 64cm. Winter travel should account for significant snow cover.

Janesville is relatively calm, with an average annual wind speed of 2km/h. For context, sustained winds below 12km/h are generally light, while anything above 25km/h is considered strong. The windiest month is June, averaging 3km/h, though still comfortable for most outdoor activities. The calmest conditions occur in December, with average winds dropping to 2km/h, making it an ideal period for wind-sensitive activities. There is moderate seasonal variation in wind speed, with a 1km/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 32°C, while the coldest stretch bottoms out in December near -4°C. Summer is next, beginning on June 21, 2026 — 1 days from now.

The best time to visit Janesville is during June, July, August and September, when the weather is most comfortable for travellers. During these months, average temperatures hover around 21°C with modest rainfall averaging 9mm per month. By contrast, December can be quite cold with temperatures dropping to -4°C. With minimal rainfall expected, you can pack light and plan outdoor activities with confidence.

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.