Frost Dates for 52601 — Burlington, Iowa

Half of springs at Burlington Municipal Airport, IA see their last 32°F night by April 15; only one in ten is past it by April 2, and one in ten still has one after May 1. Planting tender crops after April 22 leaves a 30% risk of a frost on them, after April 27 20%, and after May 1 10%. The 16 days between the even-odds date and the one-in-ten date is wider than at 95% of the 132 Iowa stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 20 in half of years, as early as October 6 one year in ten, and holds off past November 1 one year in ten. A hard freeze of 28°F follows 11 days later, around October 31; in spring the one-in-ten date for 28°F is April 22, 9 days before the 32°F one. The freeze-free season lasts 187 days in a typical year, longer than at 93% of the 132 Iowa stations; it reaches 205 days one year in ten and falls short of 165 one year in ten. On average 119 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 13 days longer, to about April 28, and return around October 11. Severe cold of 16°F or below comes every winter, usually between November 29 and March 8.

July is the warmest month at Burlington Municipal Airport, IA, averaging 85°F by day and 66°F at night; January is the coldest at 32°F and 16°F. A freezing night is all but certain in every month from November 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 12% of years.

Warmth for growing adds up to 3,554 growing degree days a year (base 50°F), more than at 95% of the 132 Iowa stations. 36% of them (1,284) have built up by the end of June, and July adds the most, 794. Precipitation totals 37.9 inches a year, most in May (4.9") and least in January (1.5"); May to September bring 56% of it.

The nearest other station, Gladstone Dam 18, IL, 7 miles northeast of Burlington and 154 feet lower, has a last frost 7 days earlier (April 8), a first frost 9 days later (October 29), a season 15 days longer.

The first measurable snow (0.1 inch or more) in Burlington usually arrives around December 1, and the last of the season around March 16. Those are the middle dates across the winters of 1991–2020 at Burlington 2S, IA, 2.7 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 30 days after the last snow.

ZIP 52601 is 2 miles from Burlington Municipal Airport, IA, which stands at 692 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 1 other ZIP code shares the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 52601 in zone 6a, the band where the coldest night of the year averaged -10 to -5°F (-23.3 to -20.6°C) over 1991–2020; a zone describes winter lows, not frost dates.