Frost Dates for 53027 — Hartford, Wisconsin

Half of springs at Hartford Wwtp, WI see their last 32°F night by May 8; only one in ten is past it by April 24, and one in ten still has one after May 24. Planting tender crops after May 14 leaves a 30% risk of a frost on them, after May 18 20%, and after May 24 10%. The 16 days between the even-odds date and the one-in-ten date is wider than at 70% of the 182 Wisconsin stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 3 in half of years, as early as September 20 one year in ten, and holds off past October 16 one year in ten. A hard freeze of 28°F follows 12 days later, around October 15; in spring the one-in-ten date for 28°F is May 12, 12 days before the 32°F one. The freeze-free season lasts 148 days in a typical year, shorter than at 69% of the 182 Wisconsin stations; it reaches 168 days one year in ten and falls short of 127 one year in ten. On average 159 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 20, and return around September 25. Severe cold of 16°F or below comes every winter, usually between November 18 and March 23.

July is the warmest month at Hartford Wwtp, WI, averaging 80°F by day and 58°F at night; January is the coldest at 26°F and 9°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 72% of years.

Warmth for growing adds up to 2,284 growing degree days a year (base 50°F), fewer than at 66% of the 182 Wisconsin stations. 32% of them (738) have built up by the end of June, and July adds the most, 595. Precipitation totals 34.1 inches a year, most in June (4.8") and least in February (1.3"); May to September bring 57% of it.

The nearest other station, Slinger Wwtp, WI, 4 miles east of Hartford, has a last frost 3 days earlier (May 5), a first frost 2 days later (October 5), a season 4 days longer.

The first measurable snow (0.1 inch or more) in Hartford usually arrives around November 27, and the last of the season around March 28. Those are the middle dates across the winters of 1991–2020 at Hartford Wwtp, WI, 2.3 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 41 days after the last snow.

ZIP 53027 is 2 miles from Hartford Wwtp, WI, which stands at 961 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 53027 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.