Frost Dates for 46148 — Knightstown, Indiana

Half of springs at New Castle 3 SW, IN see their last 32°F night by April 27; only one in ten is past it by April 11, and one in ten still has one after May 12. Planting tender crops after May 3 leaves a 30% risk of a frost on them, after May 7 20%, and after May 12 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 17 in half of years, as early as October 4 one year in ten, and holds off past October 28 one year in ten. A hard freeze of 28°F follows 10 days later, around October 27; in spring the one-in-ten date for 28°F is May 3, 9 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 192 days one year in ten and falls short of 151 one year in ten. On average 132 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 9 days longer, to about May 6, and return around October 7. Severe cold of 16°F or below comes every winter, usually between December 1 and March 14.

July is the warmest month at New Castle 3 SW, IN, averaging 83°F by day and 61°F at night; January is the coldest at 34°F and 17°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 39% of years.

Warmth for growing adds up to 3,058 growing degree days a year (base 50°F), fewer than at 82% of the 125 Indiana stations. 36% of them (1,095) have built up by the end of June, and July adds the most, 684. Precipitation totals 44.4 inches a year, most in June (5.3") and least in February (2.5"); May to September bring 48% of it.

The nearest other station, Greenfield, IN, 13 miles west of Knightstown, has a last frost 8 days earlier (April 19), a first frost 5 days later (October 22), a season 12 days longer.

The first measurable snow (0.1 inch or more) in Knightstown usually arrives around December 2, and the last of the season around March 13. Those are the middle dates across the winters of 1991–2020 at Knightstown 2ENE, IN, 1.5 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 45 days after the last snow.

ZIP 46148 is 9 miles from New Castle 3 SW, IN, which stands at 991 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 47362 (New Castle). The 2023 USDA Plant Hardiness Zone Map lists ZIP 46148 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.