Your nature year
Janesville, Wisconsinthrough the year
When do frost, green-up and fall color come to Janesville?
For a day trip, Necedah Refuge is 111 miles off; its spring migration is with May (local timing). For fall foliage, the nearest is Indiana Dunes (124 mi, usually Oct 11–20).
The town is about 839 feet above sea level. Expect about 172 frost-free days in Janesville: the last spring frost usually comes around Apr 26, the first fall one around Oct 15, going by NOAA's Afton - Janesville Wwtp station 4.2 miles away. About 4 weeks pass between first leaf and first bloom here. Spring green-up reaches town around Apr 11, with first blooms around May 10. Within 150 miles we follow 3 places, out to Port Louisa Refuge 149 miles to the southwest. Across Wisconsin, fall color is usually well under way by early October.
Updated Sep 29. Sources: US Census Bureau, 2024 Gazetteer (places) ↗ (opens in a new tab), US Census Bureau, city and town population estimates, 2024 ↗ (opens in a new tab), NOAA NCEI U.S. Climate Normals 1991–2020 (annual/seasonal) ↗ (opens in a new tab)
Janesville's year at a glance
- Frost possible
- Frost-free, ~Apr 26 to ~Oct 15
- First leaf ~Apr 11
- First bloom ~May 10
- Fall color under way ~Oct 8 (WI)
- Today
Near Janesville right now
- Fall color is usually well under way by early October in WisconsinStatewide · USA-NPN volunteer observations, 2020–2025 · not a forecast~9 days
- First fall frost usually around Oct 15 · last spring frost around Apr 26NOAA 1991–2020 normals, Afton - Janesville Wwtp (4.2 mi, 50% dates)~2 weeks
- Fall foliage · Indiana Dunes · 124 miusually Oct 11–20~12 days
Janesville's nature year
- Apr: Spring green-upApr
- Apr: Last spring frostApr
- May: Spring migration · Necedah RefugeMay
- Oct: Fall color (WI)Oct
- Oct: First fall frostOct
Nearby, season by season
Fall foliage
- Indiana Dunes · 124 miusually Oct 11–20~12 days
Spring migration
- Necedah Refuge · 111 miLocal timing: with May~7 months
- Port Louisa Refuge · 149 miLocal timing: Apr 1–May 31~6 months
Snow in Janesville
Snow usually becomes possible around Nov 30 (our calculation from NOAA's daily snow chances: the first day the chance of 0.1" or more of snow reaches 10%). NOAA's normals at Afton - Janesville Wwtp (4.2 mi away): 37 inches of snow in an average year, about 12.7 days with 1 inch or more.
NOAA's chance of at least 0.1 inch of snow on each date (one value per week, September to May), averaged over 1991–2020. A typical year, not a forecast.
Frost and green-up
Last spring frost
Apr 26
Average (50% date)
First fall frost
Oct 15
About 172 days without frost between
Spring green-up
Apr 11
First bloom around May 10
Frost: NOAA 1991–2020 climate normals at Afton - Janesville Wwtp (4.2 mi from Janesville), the day a 32 °F night is as likely as not. Green-up: the USA-NPN Spring Index, 1991–2020 average at the town.
Questions people ask
When is the first frost in Janesville?
On average around Oct 15, and the last spring frost around Apr 26: about 172 days without frost between. These are NOAA's 1991–2020 normals at Afton - Janesville Wwtp, 4.2 miles away (the day a 32 °F night is as likely as not).
When does spring green-up reach Janesville?
The USA-NPN Spring Index puts first leaf around Apr 11 and first bloom around May 10, on average for 1991–2020 at the town.
Where can I see fall foliage near Janesville?
Indiana Dunes, 124 miles (usually Oct 11–20). Distances are straight-line.
Where can I see spring migration near Janesville?
Necedah Refuge, 111 miles (local timing: with May); Port Louisa Refuge, 149 miles (local timing: Apr 1–May 31). Distances are straight-line.
When does it start snowing in Janesville?
Snow usually becomes possible around Nov 30: our calculation from NOAA's daily snow chances: the first day the chance of 0.1" or more of snow reaches 10%, at Afton - Janesville Wwtp. An average year brings 37 inches (NOAA 1991–2020). A typical year, not a forecast.Sources: NOAA NCEI U.S. Climate Normals 1991–2020 (annual/seasonal snowfall) ↗ (opens in a new tab), NOAA NCEI U.S. Climate Normals 1991–2020 (daily snowfall probabilities) ↗ (opens in a new tab)
How we know
US Census Bureau, 2024 Gazetteer (places) (opens in a new tab) (Sep 27) · US Census Bureau, city and town population estimates, 2024 (opens in a new tab) (Sep 27) · NOAA NCEI U.S. Climate Normals 1991–2020 (annual/seasonal) (opens in a new tab) (Sep 27) · USA National Phenology Network, Spring Index 1991–2020 averages (opens in a new tab) (Sep 27) · USA National Phenology Network, colored leaves observations (opens in a new tab) (Sep 29)