Frost Dates for 50208 — Newton, Iowa

Half of springs at Newton, IA see their last 32°F night by April 22; only one in ten is past it by April 8, and one in ten still has one after May 4. Planting tender crops after April 28 leaves a 30% risk of a frost on them, after May 1 20%, and after May 4 10%. The 12 days between the even-odds date and the one-in-ten date is narrower than at 67% of the 132 Iowa stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 17 in half of years, as early as October 1 one year in ten, and holds off past October 28 one year in ten. A hard freeze of 28°F follows 9 days later, around October 26; in spring the one-in-ten date for 28°F is April 25, 9 days before the 32°F one. The freeze-free season lasts 174 days in a typical year, longer than at 79% of the 132 Iowa stations; it reaches 193 days one year in ten and falls short of 157 one year in ten. On average 142 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 10 days longer, to about May 2, and return around October 4. Severe cold of 16°F or below comes every winter, usually between November 20 and March 17.

July is the warmest month at Newton, IA, averaging 85°F by day and 64°F at night; January is the coldest at 28°F and 10°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From June to September the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 21% of years.

Warmth for growing adds up to 3,112 growing degree days a year (base 50°F), more than at 62% of the 132 Iowa stations. 35% of them (1,084) have built up by the end of June, and July adds the most, 750. Precipitation totals 35.1 inches a year, most in June (5.0") and least in January (0.9"); May to September bring 62% of it.

The nearest other station, Grinnell 3 SW, IA, 15 miles east of Newton, has a last frost 11 days later (May 3), a first frost 11 days earlier (October 6), a season 19 days shorter.

The first measurable snow (0.1 inch or more) in Newton usually arrives around November 29, and the last of the season around March 20. Those are the middle dates across the winters of 1991–2020 at Newton, IA, 1 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 50208 is 1 mile from Newton, IA, which stands at 960 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 50208 in zone 5b, the band where the coldest night of the year averaged -15 to -10°F (-26.1 to -23.3°C) over 1991–2020; a zone describes winter lows, not frost dates.