Frost Dates
Frost Dates · Washington

Frost dates for Spokane, Washington

Washington · first & last freeze, from NOAA 1991–2020 climate normals

Typical last spring freeze (32°F)
April 26
median date, 1991–2020
Typical first fall freeze (32°F)
October 15
median date, 1991–2020
Typical frost-free season
172 days
between the median dates

In a typical year, the last spring freeze around Spokane comes near April 26 and the first fall freeze near October 15. One year in ten, a freeze still arrives after May 10 in spring — and one year in ten, the first fall freeze has already landed by September 30. NCEI's own growing-season statistic (days between freezes, percentiled per year) puts the median at 170 days.

JFMAMJJASONDApril 26October 15
The year at a glance: blue bands span the 9-in-10 to 1-in-10 range where the last spring / first fall 32°F freeze lands; the green band is the typical frost-free window between the median dates. Measured at Spokane Felts Fld, WA (USW00094176), 5.3 mi from the city's census reference point, elev. 1,953 ft. NOAA/NCEI 1991–2020 normals.

Freeze-date probabilities, three thresholds

ThresholdLast spring — 9 in 10 years past byLast spring — typical (median)Last spring — 1 in 10 years later thanFirst fall — 1 in 10 years byFirst fall — typical (median)First fall — 9 in 10 years by
36°F — near-freezing (frost can occur)April 27May 9May 25September 19October 1October 15
32°F — freezingApril 10April 26May 10September 30October 15October 31
28°F — hard freezeMarch 16April 4April 26October 11October 27November 13

Measured at Spokane Felts Fld, WA (USW00094176), 5.3 mi from the city's census reference point, elev. 1,953 ft. NOAA/NCEI 1991–2020 normals. Read each date column as odds over the 30-year record — e.g. "9 in 10 years past by" means only one spring in ten saw a later freeze than that date.

Frost-free windows (computed)

Window (32°F ends)OpensClosesLength
Cautious (1-in-10 freeze risk at each end)May 10September 30143 days
Typical (median freeze dates)April 26October 15172 days
Gambler's (9-in-10 freeze risk at each end)April 10October 31204 days

Pure arithmetic on the freeze-date percentiles above — the "cautious" window opens on the date only 1 year in 10 still sees a later spring freeze, and closes on the date by which only 1 year in 10 has already frozen.

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