Frost Dates for 98338 — Graham, Washington

Half of springs at Mcmillin Rsvr, WA see their last 32°F night by April 11; only one in ten is past it by March 23, and one in ten still has one after April 29. Planting tender crops after April 19 leaves a 30% risk of a frost on them, after April 24 20%, and after April 29 10%. The 18 days between the even-odds date and the one-in-ten date is narrower than at 56% of the 113 Washington stations behind this site's ZIP pages.

In fall the first 32°F night comes by October 30 in half of years, as early as October 13 one year in ten, and holds off past November 17 one year in ten. A hard freeze of 28°F follows 15 days later, around November 14; in spring the one-in-ten date for 28°F is April 8, 21 days before the 32°F one. The freeze-free season lasts 202 days in a typical year, longer than at 63% of the 113 Washington stations; it reaches 226 days one year in ten and falls short of 177 one year in ten. On average 60 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 20 days longer, to about May 1, and return around October 12. Nights of 24°F, cold enough to damage hardier plants, come in 98% of winters and 16°F in 37%.

August is the warmest month at Mcmillin Rsvr, WA, averaging 77°F by day and 53°F at night; December is the coldest at 45°F and 33°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 75% of years.

Warmth for growing adds up to 1,715 growing degree days a year (base 50°F), fewer than at 77% of the 113 Washington stations. 28% of them (477) have built up by the end of June, and August adds the most, 451. Precipitation totals 45.2 inches a year, most in November (7.1") and least in July (0.9"); May to September bring 20% of it.

The nearest other station, Tacoma #1, WA, 16 miles north of Graham and 554 feet lower, has a last frost 34 days earlier (March 8), a first frost 15 days later (November 14), a season 48 days longer.

The first measurable snow (0.1 inch or more) in Graham usually arrives around December 21, and the last of the season around February 23. Those are the middle dates across the winters of 1991–2020 at Mcmillin Rsvr, WA, 7.6 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 47 days after the last snow.

ZIP 98338 is 8 miles from Mcmillin Rsvr, WA, which stands at 579 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 13 other ZIP codes share the station; its figures are presented in full for 98391 (Bonney Lake). The 2023 USDA Plant Hardiness Zone Map lists ZIP 98338 in zone 8b, the band where the coldest night of the year averaged 15 to 20°F (-9.4 to -6.7°C) over 1991–2020; a zone describes winter lows, not frost dates.