Frost Dates for 99323 — Burbank, Washington

Half of springs at Ice Harbor Dam, WA see their last 32°F night by April 7; only one in ten is past it by March 20, and one in ten still has one after April 30. Planting tender crops after April 17 leaves a 30% risk of a frost on them, after April 23 20%, and after April 30 10%. The 23 days between the even-odds date and the one-in-ten date is wider than at 81% of the 113 Washington 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 October 22 in half of years, as early as October 6 one year in ten, and holds off past November 9 one year in ten. A hard freeze of 28°F follows 13 days later, around November 4; in spring the one-in-ten date for 28°F is April 7, 23 days before the 32°F one. The freeze-free season lasts 199 days in a typical year, longer than at 57% of the 113 Washington stations; it reaches 223 days one year in ten and falls short of 172 one year in ten. On average 84 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 18 days longer, to about April 25, and return around October 10. Nights of 24°F, cold enough to damage hardier plants, come in 100% of winters and 16°F in 90%.

July is the warmest month at Ice Harbor Dam, WA, averaging 89°F by day and 61°F at night; January is the coldest at 42°F and 29°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 65% of years.

Warmth for growing adds up to 3,172 growing degree days a year (base 50°F), more than at 96% of the 113 Washington stations. 32% of them (1,004) have built up by the end of June, and July adds the most, 770. Precipitation totals 11.2 inches a year, most in January (1.4") and least in July (0.3"); May to September bring 28% of it.

The nearest other station, Kennewick, WA, 11 miles west of Burbank, has a last frost 10 days earlier (March 28), a first frost 8 days later (October 30), a season 17 days longer.

Measurable snow is rare here: only 9 of 21 winters from 1991 to 2020 recorded 0.1 inch or more at Ice Harbor Dam, WA, 3.7 miles away, so there is no typical first-snow date to plan around.

ZIP 99323 is 4 miles from Ice Harbor Dam, WA, which stands at 368 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. The 2023 USDA Plant Hardiness Zone Map lists ZIP 99323 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.