Frost Dates for 51351 — Milford, Iowa

Half of springs at Milford 4 NW, IA see their last 32°F night by May 1; 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 5 leaves a 30% risk of a frost on them, after May 9 20%, and after May 14 10%. The 13 days between the even-odds date and the one-in-ten date is narrower than at 42% of the 132 Iowa stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 6 in half of years, as early as September 24 one year in ten, and holds off past October 21 one year in ten. A hard freeze of 28°F follows 11 days later, around October 17; in spring the one-in-ten date for 28°F is May 4, 10 days before the 32°F one. The freeze-free season lasts 158 days in a typical year, shorter than at 76% of the 132 Iowa stations; it reaches 177 days one year in ten and falls short of 140 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 8 days longer, to about May 9, and return around September 28. Severe cold of 16°F or below comes every winter, usually between November 11 and March 27.

July is the warmest month at Milford 4 NW, IA, averaging 83°F by day and 62°F at night; January is the coldest at 24°F and 8°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 2,777 growing degree days a year (base 50°F), fewer than at 78% of the 132 Iowa stations. 34% of them (938) have built up by the end of June, and July adds the most, 697. Precipitation totals 29.5 inches a year, most in June (4.5") and least in January (0.7"); May to September bring 64% of it.

The nearest other station, Spirit Lake, IA, 6 miles north of Milford, has a last frost 3 days earlier (April 28), a first frost 5 days later (October 11), a season 6 days longer.

The first measurable snow (0.1 inch or more) in Milford usually arrives around November 20, and the last of the season around March 24. Those are the middle dates across the winters of 1991–2020 at Milford 4 NW, IA, 3.7 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 38 days after the last snow.

ZIP 51351 is 4 miles from Milford 4 NW, IA, which stands at 1,402 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 51351 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.