Frost Dates for 46239 — Indianapolis, Indiana

Half of springs at Indianapolis SE Side, IN see their last 32°F night by April 20; only one in ten is past it by April 6, and one in ten still has one after May 5. Planting tender crops after April 26 leaves a 30% risk of a frost on them, after April 30 20%, and after May 5 10%. The 15 days between the even-odds date and the one-in-ten date is narrower than at 70% of the 125 Indiana stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 21 in half of years, as early as October 7 one year in ten, and holds off past November 3 one year in ten. A hard freeze of 28°F follows 11 days later, around November 1; in spring the one-in-ten date for 28°F is April 23, 12 days before the 32°F one. The freeze-free season lasts 183 days in a typical year, longer than at 54% of the 125 Indiana stations; it reaches 203 days one year in ten and falls short of 163 one year in ten. On average 120 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 April 30, and return around October 11. Severe cold of 16°F or below comes every winter, usually between December 4 and March 6.

July is the warmest month at Indianapolis SE Side, IN, averaging 84°F by day and 64°F at night; January is the coldest at 34°F and 19°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 18% of years.

Warmth for growing adds up to 3,384 growing degree days a year (base 50°F), more than at 51% of the 125 Indiana stations. 36% of them (1,228) have built up by the end of June, and July adds the most, 746. Precipitation totals 44.6 inches a year, most in June (5.4") and least in February (2.3"); May to September bring 47% of it.

The nearest other station, Castleton 2 S, IN, 11 miles north of Indianapolis, has a last frost 2 days earlier (April 18), a first frost 5 days later (October 26), a season 7 days longer.

The first measurable snow (0.1 inch or more) in Indianapolis usually arrives around December 14, and the last of the season around March 4. Those are the middle dates across the winters of 1991–2020 at Indianapolis SE Side, IN, 3.8 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 47 days after the last snow.

ZIP 46239 is 4 miles from Indianapolis SE Side, IN, which stands at 845 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 12 other ZIP codes share the station; its figures are presented in full for 46143 (Greenwood). The 2023 USDA Plant Hardiness Zone Map lists ZIP 46239 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.