USDA Hardiness Zone 8b
Frost Dates for 98274 — Mount Vernon, Washington
Averages from Mt Vernon 3 Wnw, Wa US, the nearest reporting station, 8.1 miles away.
Plant tender crops after March 24, and expect the first autumn freeze around November 3. That leaves about 224 frost-free days.
- Last spring frost
- March 24
- First fall frost
- November 3
- Growing season
- 224 days
- Hardiness zone
- 8b
50% probability
50% probability
frost-free
15 to 20°F annual low
Planting calendar for 98274
| When | What to do |
|---|---|
| January 13 – January 27 | Start peppers and aubergines indoors They need eight to ten weeks under lights before they can go out. |
| January 27 – February 10 | Start tomatoes indoors Six to eight weeks gives a transplant big enough to set fruit early. |
| February 24 – March 10 | Sow peas, spinach, lettuce, radish outdoors These tolerate light frost and prefer to germinate in cool soil. |
| March 24 onward | Transplant tomatoes, peppers, basil, squash, cucumbers The average last freeze has passed — still watch the actual forecast. |
| by August 11 | Sow the autumn crop of carrots, beets and brassicas They need about twelve weeks to size up before growth stops. |
| by October 20 | Harvest tender crops, or be ready to cover them A first freeze two weeks early is well within normal variation. |
| November 3 onward | Plant garlic, mulch beds, lift tender bulbs Garlic wants a cold spell; bare soil loses structure over winter. |
What these dates mean
Wait until after March 24 to put tender plants — tomatoes, peppers, basil, squash — in the ground. That is the date by which half of years in Mount Vernon, Washington are past their last freeze. Harvest before November 3, which leaves roughly 224 frost-free days.
ZIP 98274 sits in USDA hardiness zone 8b, meaning the average coldest night of the year falls between 15 to 20°F. Zone decides what survives the winter; frost dates decide when to plant each spring. They are different questions, and a plant can pass one and fail the other.
These are thirty-year NOAA averages for 1991–2020, not a forecast. Any individual year can frost two to three weeks either side of these dates, so check the actual forecast before planting out.