Frost Dates for 97828 — Enterprise, Oregon

Half of springs at Enterprise 20 NNE, OR see their last 32°F night by June 8; only one in ten is past it by May 18, and one in ten still has one after July 8. Planting tender crops after June 20 leaves a 30% risk of a frost on them, after June 30 20%, and after July 8 10%. The 30 days between the even-odds date and the one-in-ten date is wider than at 87% of the 103 Oregon stations behind this site's ZIP pages, so a fixed calendar date is a gamble here.

In fall the first 32°F night comes by September 5 in half of years, as early as August 16 one year in ten, and holds off past September 22 one year in ten. A hard freeze of 28°F follows 17 days later, around September 22; in spring the one-in-ten date for 28°F is June 5, 33 days before the 32°F one. The freeze-free season lasts 84 days in a typical year, the shortest of the 103 Oregon stations; it reaches 115 days one year in ten and falls short of 56 one year in ten. On average 204 nights a year drop to 32°F or below. Severe cold of 16°F or below comes every winter, usually between November 5 and March 12.

July is the warmest month at Enterprise 20 NNE, OR, averaging 88°F by day and 45°F at night; December is the coldest at 36°F and 18°F. A freezing night is all but certain in every month from September to May (a 90% chance or more). No month is safe from a 32°F night: even the warmest has at least a 10% chance. In spring, June still brings one in 59% of years and July still brings one in 19% of years.

Warmth for growing adds up to 1,750 growing degree days a year (base 50°F), fewer than at 76% of the 103 Oregon stations. 25% of them (439) have built up by the end of June, and July adds the most, 513. Precipitation totals 18.9 inches a year, most in November (2.3") and least in August (0.7"); May to September bring 34% of it.

The nearest other station, Joseph, OR, 14 miles south of Enterprise and 904 feet higher, has a last frost 15 days earlier (May 24), a first frost 26 days later (October 1), a season 42 days longer.

The first measurable snow (0.1 inch or more) in Enterprise usually arrives around November 8, and the last of the season around April 1. Those are the middle dates across the winters of 1991–2020 at Wallowa, OR, 12.8 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 68 days after the last snow.

ZIP 97828 is 13 miles from Enterprise 20 NNE, OR, which stands at 3,280 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 97828 in zone 7a, the band where the coldest night of the year averaged 0 to 5°F (-17.8 to -15.0°C) over 1991–2020; a zone describes winter lows, not frost dates.