When to plant in Hillsboro, OR
USDA Zone 8bHere are the average frost dates, USDA hardiness zone, and a month-by-month planting calendar for Hillsboro, Oregon — all computed from Hillsboro's nearest NOAA weather station.
Zone 8b means many perennials and even some tender shrubs overwinter in Hillsboro, while your frost dates still decide when annuals go out.
Frost probability
PORTLAND-HILLSBORO 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 Hillsboro’s own odds, recorded at PORTLAND-HILLSBORO AP.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | May 27 | May 5 | Apr 21 | Sep 20 | Oct 6 | Oct 31 |
| 32°F | May 3 | Apr 16 | Mar 25 | Oct 3 | Oct 23 | Nov 18 |
| 28°F | Apr 9 | Mar 13 | Feb 15 | Oct 20 | Nov 12 | Dec 10 |
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 Hillsboro, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
3 within 12 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.
Hillsboro planting FAQ
When is the last spring frost in Hillsboro, OR?
On average, the last spring frost in Hillsboro is around April 16 (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 Hillsboro, OR?
In Hillsboro, the first 32°F freeze of fall lands around October 23 on average. Time your last harvests and any season-extension cover before it.
What hardiness zone is Hillsboro in?
Hillsboro is in USDA hardiness zone 8b. In zone 8b, winters are mild — many tender perennials overwinter here.
How long is the growing season in Hillsboro?
There are roughly 190 frost-free days in Hillsboro (a moderate growing season), running from the average last frost around April 16 to the first fall frost near October 23.
When should I plant tomatoes in Hillsboro?
In Hillsboro, start tomato seeds indoors around February 19–March 5, then transplant seedlings outdoors around April 23 once the danger of frost has passed.
Never miss a window in Hillsboro
An email when it’s time to start seeds, transplant, and sow — timed to Hillsboro’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reach- Aloha · 6 km
- Oak Hills · 7 km
- Bethany · 9 km
- Cornelius · 9 km
- Cedar Mill · 11 km
- Beaverton · 11 km
- Forest Grove · 14 km
- Tigard · 16 km
Frost dates recorded at PORTLAND-HILLSBORO 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 Hillsboro, OR — Frost Dates & Zone 8b." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USW00094261. Retrieved from https://blissgarden.com/oregon/hillsboro.