Zillah, WA 98921 Frost Dates
Zillah, WA: when does the frost end?
Around 05/04 is the usual last spring frost, about 249 days away. Fall's first freeze usually shows up around 10/10, roughly 155 days after the last spring frost.
Zillah sits in USDA Zone 7a (0 to 5°F average annual minimum). The dates above are NOAA's 1991-2020 normal at the nearest reporting station, a 30-year average, not a forecast.
Stretching the season past the first frost
With roughly 6 weeks until Zillah's first fall frost, a row cover or cold frame is what stretches the last few weeks of harvest here.
The actual range around Zillah's last frost
05/04 is the middle of 30 years of NOAA records, not a promise. Getting tender plants in by 04/21 carries real risk, frost has hit that late in about 9 of 10 years here. Wait until 05/23 and only about 1 year in 10 sees frost after that.
Zillah against the rest of the dataset
Zillah's growing season runs about 155 days, ranking 33,979 of 40,283 US ZIP codes measured here, longest to shortest. Within WA, it ranks 584 of 700.
Learn more
Before leaning on 98921's figures: zone vs. frost date explains why Zone 7a and Zillah's frost date answer different questions, while the frost range explains how to read the range around Zillah's dates instead of trusting one.