Frost Dates for 50595 — Webster City, Iowa

Half of springs at Webster City, IA see their last 32°F night by May 3; only one in ten is past it by April 20, and one in ten still has one after May 16. Planting tender crops after May 8 leaves a 30% risk of a frost on them, after May 11 20%, and after May 16 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 2 in half of years, as early as September 18 one year in ten, and holds off past October 16 one year in ten. A hard freeze of 28°F follows 10 days later, around October 12; in spring the one-in-ten date for 28°F is May 7, 9 days before the 32°F one. The freeze-free season lasts 150 days in a typical year, shorter than at 97% of the 132 Iowa stations; it reaches 169 days one year in ten and falls short of 131 one year in ten. On average 160 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 11, and return around September 23. Severe cold of 16°F or below comes every winter, usually between November 9 and March 27.

July is the warmest month at Webster City, IA, averaging 83°F by day and 61°F at night; January is the coldest at 26°F and 7°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 63% of years.

Warmth for growing adds up to 2,678 growing degree days a year (base 50°F), fewer than at 87% of the 132 Iowa stations. 34% of them (917) have built up by the end of June, and July adds the most, 676. Precipitation totals 37.5 inches a year, most in June (5.8") and least in January (0.9"); May to September bring 63% of it.

The nearest other station, Clarion, IA, 18 miles north of Webster City, has a last frost 3 days earlier (April 30), a first frost 8 days later (October 10), a season 12 days longer.

The first measurable snow (0.1 inch or more) in Webster City usually arrives around November 23, and the last of the season around March 31. Those are the middle dates across the winters of 1991–2020 at Webster City, IA, 1.2 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 33 days after the last snow.

ZIP 50595 is 1 mile from Webster City, IA, which stands at 1,072 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 50595 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.