Frost Dates for 48820 — Dewitt, Michigan

Half of springs at Lansing Capital City Airport, MI see their last 32°F night by May 1; only one in ten is past it by April 18, and one in ten still has one after May 18. Planting tender crops after May 7 leaves a 30% risk of a frost on them, after May 11 20%, and after May 18 10%. The 17 days between the even-odds date and the one-in-ten date is wider than at 62% of the 172 Michigan stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 13 in half of years, as early as September 29 one year in ten, and holds off past October 28 one year in ten. A hard freeze of 28°F follows 14 days later, around October 27; in spring the one-in-ten date for 28°F is May 6, 12 days before the 32°F one. The freeze-free season lasts 162 days in a typical year, longer than at 60% of the 172 Michigan stations; it reaches 183 days one year in ten and falls short of 141 one year in ten. On average 143 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 12 days longer, to about May 13, and return around October 1. Severe cold of 16°F or below comes every winter, usually between December 1 and March 19.

July is the warmest month at Lansing Capital City Airport, MI, averaging 83°F by day and 61°F at night; January is the coldest at 31°F and 17°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 52% of years.

Warmth for growing adds up to 2,748 growing degree days a year (base 50°F), more than at 79% of the 172 Michigan stations. 33% of them (919) have built up by the end of June, and July adds the most, 677. Precipitation totals 33.5 inches a year, most in June (3.8") and least in February (1.7"); May to September bring 50% of it.

The nearest other station, Saint Johns, MI, 12 miles north of Dewitt, has a last frost 3 days earlier (April 28), a first frost 11 days later (October 24), a season 17 days longer.

The first measurable snow (0.1 inch or more) in Dewitt usually arrives around November 10, and the last of the season around April 11. Those are the middle dates across the winters of 1991–2020 at Lansing Capital City Airport, MI, 4.3 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 20 days after the last snow.

ZIP 48820 is 4 miles from Lansing Capital City Airport, MI, which stands at 841 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 8 other ZIP codes share the station; its figures are presented in full for 48917 (Lansing). The 2023 USDA Plant Hardiness Zone Map lists ZIP 48820 in zone 6a, the band where the coldest night of the year averaged -10 to -5°F (-23.3 to -20.6°C) over 1991–2020; a zone describes winter lows, not frost dates.