Frost Dates for 57747 — Hot Springs, South Dakota

Half of springs at Hot Springs, SD see their last 32°F night by May 16; only one in ten is past it by May 4, and one in ten still has one after May 31. Planting tender crops after May 22 leaves a 30% risk of a frost on them, after May 26 20%, and after May 31 10%. The 15 days between the even-odds date and the one-in-ten date is wider than at 84% of the 49 South Dakota stations behind this site's ZIP pages.

In fall the first 32°F night comes by September 27 in half of years, as early as September 12 one year in ten, and holds off past October 9 one year in ten. A hard freeze of 28°F follows 10 days later, around October 7; in spring the one-in-ten date for 28°F is May 18, 13 days before the 32°F one. The freeze-free season lasts 133 days in a typical year, shorter than at 90% of the 49 South Dakota stations; it reaches 150 days one year in ten and falls short of 113 one year in ten. On average 176 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 May 29, and return around September 19. Severe cold of 16°F or below comes every winter, usually between November 4 and April 2.

July is the warmest month at Hot Springs, SD, averaging 89°F by day and 57°F at night; January is the coldest at 40°F and 14°F. A freezing night is all but certain in every month from October to May (a 90% chance or more). From June to August the chance of a 32°F night stays under 10% each month.

Warmth for growing adds up to 2,643 growing degree days a year (base 50°F), fewer than at 59% of the 49 South Dakota stations. 29% of them (774) have built up by the end of June, and July adds the most, 711. Precipitation totals 18.7 inches a year, most in May (3.3") and least in January (0.4"); May to September bring 65% of it.

The nearest other station, Custer, SD, 26 miles north of Hot Springs and 1,920 feet higher, has a last frost 2 days later (May 18), a first frost 1 day later (September 28), a season 4 days shorter.

The first measurable snow (0.1 inch or more) in Hot Springs usually arrives around November 10, and the last of the season around April 13. Those are the middle dates across the winters of 1991–2020 at Hot Springs, SD, 2.9 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 33 days after the last snow.

ZIP 57747 is 3 miles from Hot Springs, SD, which stands at 3,560 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 57747 in zone 5a, the band where the coldest night of the year averaged -20 to -15°F (-28.9 to -26.1°C) over 1991–2020; a zone describes winter lows, not frost dates.