Frost Dates for Mount Vernon, WA 98273

Last spring frost March 29 · First fall frost October 30 · 215 frost-free days · USDA Zone 8b

Frost probability for 98273

Frost10%50%90%
Spring (last frost)April 22March 29March 6
Fall (first frost)October 11October 30November 19

Dates come from NOAA 1971–2000 freeze probabilities at the nearest reporting station (14.1 km away); the 50% date is the median year.

Frost dates by ZIP code in Mount Vernon, WA

ZIPLast spring frost (50%)First fall frost (50%)Zone
98273March 29October 308b
98274April 6October 268b

Month by month in Mount Vernon

MonthWhat to do
JanuaryStart peppers and eggplant indoors 8–10 weeks before your last frost (around March 29). Start tomatoes about two weeks later, 6–8 weeks before last frost.
FebruaryStart herbs, basil, and squash indoors (4–6 weeks before frost). Direct sow peas, spinach, and lettuce if soil is workable.
MarchLast frost around March 29. Transplant cold-hardy crops (broccoli, kale, cabbage). Harden off tomato and pepper seedlings.
AprilFrost has passed. Transplant tomatoes, peppers, and basil outdoors. Direct sow beans, cucumbers, squash, and zucchini.
MaySuccession plant lettuce and greens. Keep beds weeded and watered consistently.
JuneHarvest regularly to encourage production. Monitor for pests and disease.
JulyMidsummer: harvest beans, zucchini, cucumbers. Start brassica seeds indoors for fall.
AugustDirect sow carrots and beets for fall harvest. Start fall broccoli and kale indoors.
SeptemberFirst fall frost approaching (around October 30). Transplant fall brassicas. Sow spinach, arugula, and radishes.
OctoberFirst frost around October 30. 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 215-day season

Frequently Asked Questions

What is the last frost date for Mount Vernon, WA (ZIP 98273)?

The median last spring frost date for Mount Vernon, WA (ZIP code 98273) is around March 29. 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 Mount Vernon, WA?

The median first fall frost date for Mount Vernon, WA is around October 30. 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 Mount Vernon, WA?

The frost-free growing season in Mount Vernon is about 215 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 Mount Vernon, WA?

Based on frost date patterns, Mount Vernon 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 Mount Vernon, WA?

Start tomato seeds indoors 6–8 weeks before your last frost date (around March 29). For Mount Vernon, that's roughly February 2 to February 16. Transplant outdoors 1–2 weeks after your last frost.

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