Frost Dates for 73521 — Altus, Oklahoma

Half of springs at Altus Irig Rsch Stn, OK see their last 32°F night by April 5; only one in ten is past it by March 20, and one in ten still has one after April 21. Planting tender crops after April 12 leaves a 30% risk of a frost on them, after April 16 20%, and after April 21 10%. The 16 days between the even-odds date and the one-in-ten date is narrower than at 61% of the 114 Oklahoma stations behind this site's ZIP pages.

In fall the first 32°F night comes by November 2 in half of years, as early as October 19 one year in ten, and holds off past November 16 one year in ten. A hard freeze of 28°F follows 8 days later, around November 10; in spring the one-in-ten date for 28°F is April 8, 13 days before the 32°F one. The freeze-free season lasts 210 days in a typical year, shorter than at 50% of the 114 Oklahoma stations; it reaches 233 days one year in ten and falls short of 189 one year in ten. On average 86 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 15, and return around October 24. Severe cold of 16°F or below comes in 98% of winters, usually between December 18 and February 16.

July is the warmest month at Altus Irig Rsch Stn, OK, averaging 97°F by day and 71°F at night; January is the coldest at 54°F and 25°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 66% of years.

Warmth for growing adds up to 5,448 growing degree days a year (base 50°F), more than at 85% of the 114 Oklahoma stations. 38% of them (2,097) have built up by the end of June, and July adds the most, 1,057. Precipitation totals 27.8 inches a year, most in May (4.1") and least in February (1.1"); May to September bring 58% of it.

The nearest other station, Mangum, OK, 20 miles northwest of Altus and 215 feet higher, has a last frost 3 days later (April 8), the same first-frost date, a season 3 days shorter.

The first measurable snow (0.1 inch or more) in Altus usually arrives around December 24, and the last of the season around February 11. Those are the middle dates across the winters of 1991–2020 at Altus Irig Rsch Stn, OK, 3.5 miles away: half of years saw snow earlier, half later. Snow fell in 80% of those winters. The last 32°F night of spring typically comes 53 days after the last snow.

ZIP 73521 is 4 miles from Altus Irig Rsch Stn, OK, which stands at 1,380 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 73521 in zone 7b, the band where the coldest night of the year averaged 5 to 10°F (-15.0 to -12.2°C) over 1991–2020; a zone describes winter lows, not frost dates.