Frost Dates for 56048 — Janesville, Minnesota

Half of springs at Waseca S Rsch & Outreach Ctr, MN see their last 32°F night by May 2; only one in ten is past it by April 17, and one in ten still has one after May 14. Planting tender crops after May 6 leaves a 30% risk of a frost on them, after May 9 20%, and after May 14 10%. The 12 days between the even-odds date and the one-in-ten date is narrower than at 85% of the 142 Minnesota stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 4 in half of years, as early as September 20 one year in ten, and holds off past October 17 one year in ten. A hard freeze of 28°F follows 10 days later, around October 14; in spring the one-in-ten date for 28°F is May 3, 11 days before the 32°F one. The freeze-free season lasts 155 days in a typical year, longer than at 64% of the 142 Minnesota stations; it reaches 175 days one year in ten and falls short of 136 one year in ten. On average 162 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 7 days longer, to about May 9, and return around September 26. Severe cold of 16°F or below comes every winter, usually between November 11 and March 26.

July is the warmest month at Waseca S Rsch & Outreach Ctr, MN, averaging 81°F by day and 61°F at night; January is the coldest at 22°F and 5°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From June to August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 56% of years.

Warmth for growing adds up to 2,635 growing degree days a year (base 50°F), more than at 74% of the 142 Minnesota stations. 34% of them (909) have built up by the end of June, and July adds the most, 662. Precipitation totals 38.0 inches a year, most in June (5.4") and least in February (1.2"); May to September bring 62% of it.

The nearest other station, Mankato, MN, 16 miles west of Janesville and 303 feet lower, has a last frost 2 days earlier (April 30), a first frost 5 days later (October 9), a season 6 days longer.

The first measurable snow (0.1 inch or more) in Janesville usually arrives around November 6, and the last of the season around April 9. Those are the middle dates across the winters of 1991–2020 at Waseca S Rsch & Outreach Ctr, MN, 9.5 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 23 days after the last snow.

ZIP 56048 is 10 miles from Waseca S Rsch & Outreach Ctr, MN, which stands at 1,153 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 3 other ZIP codes share the station; its figures are presented in full for 56093 (Waseca). The 2023 USDA Plant Hardiness Zone Map lists ZIP 56048 in zone 5a, the band where the coldest night of the year averaged -20 to -15°F (-28.9 to -26.1°C) over 1991–2020; a zone describes winter lows, not frost dates.