Frost Dates for 51054 — Sergeant Bluff, Iowa

Half of springs at Sioux City Gateway Airport, IA see their last 32°F night by April 29; only one in ten is past it by April 16, and one in ten still has one after May 14. Planting tender crops after May 4 leaves a 30% risk of a frost on them, after May 8 20%, and after May 14 10%. The 15 days between the even-odds date and the one-in-ten date is wider than at 82% of the 132 Iowa stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 5 in half of years, as early as September 22 one year in ten, and holds off past October 18 one year in ten. A hard freeze of 28°F follows 10 days later, around October 15; in spring the one-in-ten date for 28°F is May 3, 11 days before the 32°F one. The freeze-free season lasts 159 days in a typical year, shorter than at 73% of the 132 Iowa stations; it reaches 177 days one year in ten and falls short of 140 one year in ten. On average 154 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 7, and return around September 28. Severe cold of 16°F or below comes every winter, usually between November 11 and March 20.

July is the warmest month at Sioux City Gateway Airport, IA, averaging 85°F by day and 63°F at night; January is the coldest at 30°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 August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 43% of years.

Warmth for growing adds up to 3,077 growing degree days a year (base 50°F), more than at 59% of the 132 Iowa stations. 35% of them (1,087) have built up by the end of June, and July adds the most, 750. Precipitation totals 29.5 inches a year, most in June (4.4") and least in January (0.7"); May to September bring 62% of it.

The nearest other station, Sioux City Ang, IA, 2 miles west of Sergeant Bluff, has the same 50% last-frost date, a first frost 2 days later (October 7), a season 2 days longer.

The first measurable snow (0.1 inch or more) in Sergeant Bluff usually arrives around November 7, and the last of the season around April 8. Those are the middle dates across the winters of 1991–2020 at Sioux City Gateway Airport, IA, 1.9 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 21 days after the last snow.

ZIP 51054 is 2 miles from Sioux City Gateway Airport, IA, which stands at 1,095 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 51054 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.