USDA Hardiness Zone 9a
Frost Dates for 98148 — Burien, Washington
Averages from Seattle Tacoma Intl Ap, Wa US, the nearest reporting station, 0.8 miles away.
Plant tender crops after March 2, and expect the first autumn freeze around November 23. That leaves about 266 frost-free days.
- Last spring frost
- March 2
- First fall frost
- November 23
- Growing season
- 266 days
- Hardiness zone
- 9a
50% probability
50% probability
frost-free
20 to 25°F annual low
- First snow
- December 18
- Last snow
- February 23
- Winters with snow
- 83%
- Snow per year
- 6.3"
median, 1991–2020
median, 1991–2020
15 of 18 observed
NOAA normal
When it snows in Burien, Washington
The first measurable snow (0.1 inch or more) in Burien, Washington usually arrives around December 18, and the last of the season around February 23. Those are the middle dates across the winters of 1991–2020 at Seattle Tacoma Intl Ap, Wa US: half of years saw snow earlier, half later. Snow fell in 83% of those winters.
For a gardener, snow matters less than frost: a light snow on frozen ground changes nothing, while a hard frost on an unprotected bed ends the season. Use the frost dates above for planting and the snow dates for getting hoses drained, mulch down and tender pots indoors.
Planting calendar for 98148
| When | What to do |
|---|---|
| December 22 – January 5 | Start peppers and aubergines indoors They need eight to ten weeks under lights before they can go out. |
| January 5 – January 19 | Start tomatoes indoors Six to eight weeks gives a transplant big enough to set fruit early. |
| February 2 – February 16 | Sow peas, spinach, lettuce, radish outdoors These tolerate light frost and prefer to germinate in cool soil. |
| March 2 onward | Transplant tomatoes, peppers, basil, squash, cucumbers The average last freeze has passed — still watch the actual forecast. |
| by August 31 | Sow the autumn crop of carrots, beets and brassicas They need about twelve weeks to size up before growth stops. |
| by November 9 | Harvest tender crops, or be ready to cover them A first freeze two weeks early is well within normal variation. |
| November 23 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 2 to put tender plants — tomatoes, peppers, basil, squash — in the ground. That is the date by which half of years in Burien, Washington are past their last freeze. Harvest before November 23, which leaves roughly 266 frost-free days.
ZIP 98148 sits in USDA hardiness zone 9a, meaning the average coldest night of the year falls between 20 to 25°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.