When to plant in Bryn Mawr-Skyway, WA
USDA Zone 9aBryn Mawr-Skyway, Washington frost dates, USDA zone, and a full-year planting calendar, drawn from the nearest NOAA station and tuned to the local season.
A generous ~248-day season lets Bryn Mawr-Skyway gardeners direct-sow more and still ripen long-maturity crops like melons and winter squash. In zone 9a, frost is a minor factor for Bryn Mawr-Skyway — most perennials thrive, and annual vegetables can go out early and stay late.
Frost probability
RENTON MUNI AP · 1991–2020The date the last spring and first fall frost occur, by threshold and probability. A 90% date is later in spring — and earlier in fall — than a 10% date; the 50% · 32°F row is what most gardeners plan around. These are Bryn Mawr-Skyway’s own odds, recorded at RENTON MUNI AP.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | Apr 25 | Apr 6 | Mar 21 | Oct 17 | Oct 31 | Nov 17 |
| 32°F | Mar 31 | Mar 13 | Feb 19 | Oct 29 | Nov 16 | Dec 9 |
| 28°F | Mar 6 | Feb 13 | Jan 1 | Nov 11 | Dec 6 | Jan 9 |
Download this table as CSV ↓ — every threshold and probability, plus this city’s planting-window dates.
What to plant now
TODAY · JULY 19Full-year planting calendar
Each bar is the exact window to take a planting action in Bryn Mawr-Skyway, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 8 km · complete 32°F normalsWhen stations disagree by more than a few days, that spread is real microclimate variation — elevation, water, urban heat. Judge which station best matches your own yard.
Bryn Mawr-Skyway planting FAQ
When is the last spring frost in Bryn Mawr-Skyway, WA?
On average, the last spring frost in Bryn Mawr-Skyway is around March 13 (50% probability at 32°F, from 1991–2020 NOAA normals). Wait until after this date to set out tender plants like tomatoes and peppers.
When is the first fall frost in Bryn Mawr-Skyway, WA?
The first fall frost in Bryn Mawr-Skyway typically arrives around November 16 (50% probability at 32°F). Harvest or protect frost-sensitive crops before then.
What hardiness zone is Bryn Mawr-Skyway in?
Bryn Mawr-Skyway is in USDA hardiness zone 9a. In zone 9a, winters are mild — many tender perennials overwinter here.
How long is the growing season in Bryn Mawr-Skyway?
Bryn Mawr-Skyway has about 248 frost-free days — a long growing season — between the average last spring frost (March 13) and first fall frost (November 16).
When should I plant tomatoes in Bryn Mawr-Skyway?
For Bryn Mawr-Skyway, sow tomatoes indoors about January 16–January 30 and move the seedlings out around March 20, after the last spring frost.
Never miss a window in Bryn Mawr-Skyway
An email when it’s time to start seeds, transplant, and sow — timed to Bryn Mawr-Skyway’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Tukwila · 3 km
- Renton · 4 km
- Newcastle · 7 km
- SeaTac · 7 km
- Mercer Island · 8 km
- Burien · 8 km
- White Center · 8 km
- Fairwood · 9 km
Frost dates recorded at RENTON MUNI AP, 2 km from the city center · 1991–2020 NOAA climate normals · zone from the USDA/PRISM 2023 map. How we compute this.
BlissGarden. "When to Plant in Bryn Mawr-Skyway, WA — Frost Dates & Zone 9a." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USW00094248. Retrieved from https://blissgarden.com/washington/bryn-mawr-skyway.