Maple Valley, WA 98038 Frost Dates
Maple Valley, WA: when does the frost end?
Typically, the last spring freeze lands around 04/20, roughly 235 days out. Fall's first freeze usually shows up around 10/25, roughly 187 days after the last spring frost.
Zone 8b (15 to 20°F average annual minimum) comes from the USDA Plant Hardiness Zone Map; the frost dates above are the 1991-2020 normal at the nearest reporting NOAA station for Maple Valley, not a forecast for this year.
Stretching the season past the first frost
With roughly 8 weeks until Maple Valley's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
Why 04/20 isn't a guarantee
04/20 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 03/31 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/10 and only about 1 year in 10 sees frost after that.
Maple Valley against the rest of the dataset
Maple Valley's growing season runs about 187 days, ranking 22,294 of 40,283 US ZIP codes measured here, longest to shortest. Within WA, it ranks 418 of 700.
Learn more
Before leaning on 98038's figures: zone vs. frost date explains why Zone 8b and Maple Valley's frost date answer different questions, while the frost range explains how to read the range around Maple Valley's dates instead of trusting one.