Frost Dates for Sammamish, WA 98074

Last spring frost April 19 · First fall frost October 21 · 185 frost-free days · USDA Zone 8b

Frost probability for 98074

Frost10%50%90%
Spring (last frost)May 11April 19March 28
Fall (first frost)October 3October 21November 8

Dates come from NOAA 1971–2000 freeze probabilities at the nearest reporting station (18.0 km away); the 50% date is the median year.

Frost dates by ZIP code in Sammamish, WA

ZIPLast spring frost (50%)First fall frost (50%)Zone
98074April 19October 218b
98075April 19October 218b

Month by month in Sammamish

MonthWhat to do
JanuaryPlan your garden layout and order seeds. Research varieties suited to your frost dates.
FebruaryStart peppers and eggplant indoors 8–10 weeks before your last frost (around April 19). Start tomatoes about two weeks later, 6–8 weeks before last frost.
MarchStart herbs, basil, and squash indoors (4–6 weeks before frost). Direct sow peas, spinach, and lettuce if soil is workable.
AprilLast frost around April 19. Transplant cold-hardy crops (broccoli, kale, cabbage). Harden off tomato and pepper seedlings.
MayFrost has passed. Transplant tomatoes, peppers, and basil outdoors. Direct sow beans, cucumbers, squash, and zucchini.
JuneSuccession plant lettuce and greens. Keep beds weeded and watered consistently.
JulyHarvest regularly to encourage production. Monitor for pests and disease.
AugustMidsummer: harvest beans, zucchini, cucumbers. Start brassica seeds indoors for fall.
SeptemberFirst fall frost approaching (around October 21). Transplant fall brassicas. Sow spinach, arugula, and radishes.
OctoberFirst frost around October 21. Harvest tomatoes and peppers before frost. Cover cold-hardy crops with row covers to extend the season.
NovemberHarvest remaining cold-hardy crops: kale, carrots, and beets. Plant garlic bulbs for next year.
DecemberClean up spent plants. Add compost to beds. Rest, review, and plan next year's garden.

What grows in a 185-day season

Frequently Asked Questions

What is the last frost date for Sammamish, WA (ZIP 98074)?

The median last spring frost date for Sammamish, WA (ZIP code 98074) is around April 19. This is the 50th-percentile date — meaning half of all years see frost end before this date. Use the 10% and 90% dates to understand the full range of risk in your area.

What is the first fall frost date in Sammamish, WA?

The median first fall frost date for Sammamish, WA is around October 21. Plan to harvest or protect frost-sensitive crops like tomatoes and peppers at least a week before this date to avoid losses.

How long is the growing season in Sammamish, WA?

The frost-free growing season in Sammamish is about 185 days. This window — from your last spring frost to your first fall frost — is when warm-season vegetables thrive. Cold-hardy crops like kale, spinach, and peas can extend your season by weeks on either side.

What USDA hardiness zone is Sammamish, WA?

Based on frost date patterns, Sammamish falls approximately in 8b. USDA hardiness zones are determined by average annual minimum winter temperatures and guide both plant selection and planting timing for your location.

When should I start tomatoes indoors in Sammamish, WA?

Start tomato seeds indoors 6–8 weeks before your last frost date (around April 19). For Sammamish, that's roughly February 23 to March 8. Transplant outdoors 1–2 weeks after your last frost.

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