Frost Dates for 98059 — Renton, Washington

Half of springs at Renton Municipal Airport, WA see their last 32°F night by March 13; only one in ten is past it by February 19, and one in ten still has one after March 31. Planting tender crops after March 22 leaves a 30% risk of a frost on them, after March 25 20%, and after March 31 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 November 16 in half of years, as early as October 29 one year in ten, and holds off past December 9 one year in ten. A hard freeze of 28°F follows 20 days later, around December 6; in spring the one-in-ten date for 28°F is March 6, 25 days before the 32°F one. The freeze-free season lasts 248 days in a typical year, longer than at 91% of the 113 Washington stations; it reaches 280 days one year in ten and falls short of 221 one year in ten. On average 30 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 24 days longer, to about April 6, and return around October 31. Nights of 24°F, cold enough to damage hardier plants, come in 71% of winters and 16°F in 6%.

August is the warmest month at Renton Municipal Airport, WA, averaging 78°F by day and 57°F at night; December is the coldest at 47°F and 37°F. A freezing night is all but certain in every month from December to February (a 90% chance or more). From April to September the chance of a 32°F night stays under 10% each month. In spring, March still brings one in 72% of years.

Warmth for growing adds up to 2,336 growing degree days a year (base 50°F), more than at 65% of the 113 Washington stations. 31% of them (719) have built up by the end of June, and August adds the most, 543. Precipitation totals 34.6 inches a year, most in November (5.6") and least in July (0.6"); May to September bring 18% of it.

The nearest other station, Kent, WA, 7 miles southwest of Renton, has a last frost 7 days later (March 20), a first frost 6 days earlier (November 10), a season 15 days shorter.

Measurable snow is rare here: only 6 of 20 winters from 1991 to 2020 recorded 0.1 inch or more at Kent, WA, 7.1 miles away, so there is no typical first-snow date to plan around.

ZIP 98059 is 3 miles from Renton Municipal Airport, WA, which stands at 29 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 6 other ZIP codes share the station; its figures are presented in full for 98058 (Renton). The 2023 USDA Plant Hardiness Zone Map lists ZIP 98059 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.