Frost Dates for 53098 — Watertown, Wisconsin

Half of springs at Watertown Wwtp, WI see their last 32°F night by April 28; only one in ten is past it by April 14, and one in ten still has one after May 13. Planting tender crops after May 3 leaves a 30% risk of a frost on them, after May 7 20%, and after May 13 10%. The 15 days between the even-odds date and the one-in-ten date is narrower than at 30% of the 182 Wisconsin stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 12 in half of years, as early as September 28 one year in ten, and holds off past October 27 one year in ten. A hard freeze of 28°F follows 13 days later, around October 25; in spring the one-in-ten date for 28°F is April 30, 13 days before the 32°F one. The freeze-free season lasts 167 days in a typical year, longer than at 79% of the 182 Wisconsin stations; it reaches 186 days one year in ten and falls short of 148 one year in ten. On average 149 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 11 days longer, to about May 9, and return around October 2. Severe cold of 16°F or below comes every winter, usually between November 24 and March 19.

July is the warmest month at Watertown Wwtp, WI, averaging 81°F by day and 61°F at night; January is the coldest at 26°F and 11°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 40% of years.

Warmth for growing adds up to 2,588 growing degree days a year (base 50°F), more than at 70% of the 182 Wisconsin stations. 33% of them (850) have built up by the end of June, and July adds the most, 657. Precipitation totals 37.4 inches a year, most in June (5.8") and least in January (1.4"); May to September bring 59% of it.

The nearest other station, Hustisford Wwtp, WI, 9 miles northeast of Watertown, has the same 50% last-frost date, a first frost 2 days earlier (October 10), a season 3 days shorter.

The first measurable snow (0.1 inch or more) in Watertown usually arrives around November 21, and the last of the season around April 6. Those are the middle dates across the winters of 1991–2020 at Watertown Wwtp, WI, 4.2 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 22 days after the last snow.

ZIP 53098 is 4 miles from Watertown Wwtp, WI, which stands at 825 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station; its figures are presented in full for 53094 (Watertown). The 2023 USDA Plant Hardiness Zone Map lists ZIP 53098 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.