Frost Dates for 46157 — Monrovia, Indiana

Half of springs at Martinsville 2 SW, IN see their last 32°F night by April 24; only one in ten is past it by April 10, and one in ten still has one after May 11. Planting tender crops after May 1 leaves a 30% risk of a frost on them, after May 5 20%, and after May 11 10%. The 17 days between the even-odds date and the one-in-ten date is wider than at 66% of the 125 Indiana stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 15 in half of years, as early as October 2 one year in ten, and holds off past October 29 one year in ten. A hard freeze of 28°F follows 11 days later, around October 26; in spring the one-in-ten date for 28°F is April 30, 11 days before the 32°F one. The freeze-free season lasts 173 days in a typical year, shorter than at 77% of the 125 Indiana stations; it reaches 191 days one year in ten and falls short of 152 one year in ten. On average 127 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 4, and return around October 6. Severe cold of 16°F or below comes every winter, usually between December 1 and March 9.

July is the warmest month at Martinsville 2 SW, IN, averaging 84°F by day and 63°F at night; January is the coldest at 36°F and 19°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 31% of years.

Warmth for growing adds up to 3,244 growing degree days a year (base 50°F), fewer than at 60% of the 125 Indiana stations. 36% of them (1,165) have built up by the end of June, and July adds the most, 722. Precipitation totals 45.5 inches a year, most in June (5.3") and least in February (2.4"); May to September bring 47% of it.

The nearest other station, Indianapolis Nwfo, IN, 17 miles northeast of Monrovia and 198 feet higher, has a last frost 12 days earlier (April 12), a first frost 12 days later (October 27), a season 23 days longer.

The first measurable snow (0.1 inch or more) in Monrovia usually arrives around December 9, and the last of the season around March 6. Those are the middle dates across the winters of 1991–2020 at Martinsville 2 SW, IN, 11.7 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 49 days after the last snow.

ZIP 46157 is 12 miles from Martinsville 2 SW, IN, which stands at 592 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 3 other ZIP codes share the station; its figures are presented in full for 46151 (Martinsville). The 2023 USDA Plant Hardiness Zone Map lists ZIP 46157 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.