When to plant in Monroe, WA
USDA Zone 8bEverything below — frost dates, hardiness zone, and what to plant when in Monroe, Washington — is derived from the closest NOAA station with complete climate normals.
Zone 8b means many perennials and even some tender shrubs overwinter in Monroe, while your frost dates still decide when annuals go out.
The average last spring frost in Monroe is now 10 days later than in the 1981–2010 normals. See how frost dates are shifting nationwide →
Frost probability
MONROE · 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 Monroe’s own odds, recorded at MONROE.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 20 | May 5 | Apr 20 | Sep 21 | Oct 6 | Oct 25 |
| 32°F | May 7 | Apr 17 | Mar 29 | Oct 7 | Oct 23 | Nov 9 |
| 28°F | Apr 14 | Mar 26 | Mar 6 | Oct 20 | Nov 8 | Nov 26 |
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 Monroe, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 20 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.
Monroe planting FAQ
When is the last spring frost in Monroe, WA?
Monroe's average last spring frost falls near April 17 — the 50% mark at 32°F in the 1991–2020 normals. Hold tender transplants until the risk has passed, then plant out.
When is the first fall frost in Monroe, WA?
Expect Monroe's first fall frost near October 23 — a 50% chance of 32°F by that date. Bring in or cover tender crops ahead of it.
What hardiness zone is Monroe in?
Monroe is in USDA hardiness zone 8b. In zone 8b, winters are mild — many tender perennials overwinter here.
How long is the growing season in Monroe?
There are roughly 189 frost-free days in Monroe (a moderate growing season), running from the average last frost around April 17 to the first fall frost near October 23.
When should I plant tomatoes in Monroe?
In Monroe, start tomato seeds indoors around February 20–March 6, then transplant seedlings outdoors around April 24 once the danger of frost has passed.
Never miss a window in Monroe
An email when it’s time to start seeds, transplant, and sow — timed to Monroe’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Maltby · 11 km
- Snohomish · 11 km
- Silver Firs · 12 km
- Cottage Lake · 14 km
- Eastmont · 15 km
- Mill Creek East · 15 km
- Bothell East · 16 km
- Woodinville · 17 km
Frost dates recorded at MONROE, 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 Monroe, WA — Frost Dates & Zone 8b." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USC00455525. Retrieved from https://blissgarden.com/washington/monroe.