Frost Dates for 46161 — Morristown, Indiana

Half of springs at Shelbyville Municipal Airport, IN see their last 32°F night by April 14; only one in ten is past it by March 31, and one in ten still has one after April 29. Planting tender crops after April 20 leaves a 30% risk of a frost on them, after April 24 20%, and after April 29 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 23 in half of years, as early as October 11 one year in ten, and holds off past November 4 one year in ten. A hard freeze of 28°F follows 11 days later, around November 3; in spring the one-in-ten date for 28°F is April 16, 13 days before the 32°F one. The freeze-free season lasts 191 days in a typical year, longer than at 72% of the 125 Indiana stations; it reaches 211 days one year in ten and falls short of 170 one year in ten. On average 106 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 24, and return around October 13. Severe cold of 16°F or below comes every winter, usually between December 9 and February 28.

July is the warmest month at Shelbyville Municipal Airport, IN, averaging 86°F by day and 65°F at night; January is the coldest at 37°F and 22°F. A freezing night is all but certain in every month from November to March (a 90% chance or more). From May to September the chance of a 32°F night stays under 10% each month. In spring, April still brings one in 87% of years.

Warmth for growing adds up to 3,784 growing degree days a year (base 50°F), more than at 74% of the 125 Indiana stations. 38% of them (1,439) have built up by the end of June, and July adds the most, 792. Precipitation totals 43.2 inches a year, most in June (5.2") and least in February (2.3"); May to September bring 46% of it.

The nearest other station, Greenfield, IN, 9 miles northwest of Morristown, has a last frost 5 days later (April 19), a first frost 1 day earlier (October 22), a season 6 days shorter.

The first measurable snow (0.1 inch or more) in Morristown usually arrives around December 7, and the last of the season around March 10. Those are the middle dates across the winters of 1991–2020 at Morristown 2 SE, IN, 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 35 days after the last snow.

ZIP 46161 is 9 miles from Shelbyville Municipal Airport, IN, which stands at 804 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 2 other ZIP codes share the station; its figures are presented in full for 46126 (Fairland). The 2023 USDA Plant Hardiness Zone Map lists ZIP 46161 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.