Gresham, Oregon: planting zone & frost dates
Gresham is in USDA plant hardiness zone 9a, where the average coldest winter night reaches 20 to 25°F (-6.7 to -3.9°C). The typical last spring frost is around Mar 27 and the first fall frost around Nov 9.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | Apr 12 | Oct 30 |
| Typical planning date (30% risk) | Mar 27 | Nov 9 |
| Median (50%) | Mar 16 | Nov 20 |
How to read this: after the spring "10% risk" date, a 32°F frost happens in only about 1 year in 10. In fall, the "10% risk" date is the early end — a frost before it happens about 1 year in 10.
Frost data comes from NOAA station PORTLAND TROUTDALE AP, OR (USW00024242), 3.7 mi (6.0 km) from the city center and 358 ft lower than the city center (-109 m). Record used for the 1991–2020 normals: 20 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Gresham
Gresham spans more than one half-zone. Share of the city's land area by zone (via its 6 ZIP codes): 9a (56%), 8b (44%). The headline zone is the one covering the most land. Look up your ZIP for your exact zone.
Vegetable planting calendar for Gresham
Dates are counted from the 30%-risk frost dates above (last frost Mar 27, first frost Nov 9). Shift a week later in cold spots or low-lying ground.
| Crop | Start indoors | Transplant / plant out | Direct sow | Fall crop sow/plant |
|---|---|---|---|---|
| Tomato | Jan 30 – Feb 13 | Apr 3 – Apr 17 | — | — |
| Pepper | Jan 16 – Jan 30 | Apr 10 – Apr 24 | — | — |
| Lettuce | Feb 13 – Feb 27 | Mar 13 – Apr 3 | Feb 27 – Apr 10 | Aug 31 – Sep 28 |
| Green Beans | — | — | Apr 3 – May 8 | Aug 17 – Aug 31 |
| Sweet Corn | — | — | Apr 3 – May 1 | — |
| Zucchini & Summer Squash | Feb 27 – Mar 6 | Apr 3 – Apr 17 | Apr 3 – Apr 24 | Aug 17 – Aug 31 |
| Cucumber | Feb 27 – Mar 6 | Apr 10 – Apr 17 | Apr 3 – Apr 24 | Aug 17 – Aug 31 |
| Carrot | — | — | Mar 6 – Apr 10 | Aug 17 – Aug 31 |
| Onion | Jan 2 – Jan 16 | Feb 27 – Mar 13 | — | — |
| Potato | — | Feb 27 – Mar 20 | — | — |
| Basil | Feb 13 – Feb 27 | Apr 10 – Apr 24 | Apr 10 – May 1 | — |
| Spinach | — | — | Feb 13 – Mar 13 | Sep 14 – Oct 12 |
| Kale | Jan 30 – Feb 13 | Feb 27 – Mar 20 | Feb 27 – Mar 20 | Aug 31 – Sep 28 |
| Broccoli | Jan 30 – Feb 13 | Mar 13 – Apr 3 | — | Aug 17 – Aug 31 |
| Peas | — | — | Feb 13 – Mar 6 | Aug 31 – Sep 14 |
| Eggplant | Jan 16 – Jan 30 | Apr 10 – Apr 24 | — | — |
| Cabbage | Jan 30 – Feb 13 | Feb 27 – Mar 13 | — | Aug 17 – Aug 31 |
| Radish | — | — | Feb 20 – Apr 10 | Sep 28 – Oct 26 |
| Strawberry | — | Feb 27 – Mar 20 | — | — |
| Beets | — | — | Mar 6 – Apr 17 | Aug 31 – Sep 14 |
Nearby cities in Oregon
- Portland — zone 9a, last frost Mar 6, first frost Nov 22
- Beaverton — zone 9a, last frost Apr 11, first frost Oct 29
- Hillsboro — zone 8b, last frost Apr 25, first frost Oct 14
- Salem — zone 8b, last frost Apr 13, first frost Oct 26
- Eugene — zone 8b, last frost Apr 25, first frost Oct 15
- Bend — zone 6b, last frost Jun 14, first frost Sep 12
More: all Oregon cities · other zone 9a cities: San Antonio, TX, Austin, TX, Seattle, WA, Las Vegas, NV, Portland, OR, Tucson, AZ, Baton Rouge, LA, Tallahassee, FL
Gresham gardening questions
When is the last frost in Gresham, OR?
Plan around Mar 27. At NOAA's Portland Troutdale Airport, OR station, 3.7 mi from the city center, there is a 30% chance of a 32°F frost after that date. Half of springs have their last frost by Mar 16, and after Apr 12 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Feb 14. Springs here are erratic: 53 days separate the 90% and 10% dates, versus a median of 36 days for cities on this site, so watch the forecast rather than the calendar.
When should I plant tomatoes in Gresham, OR?
Start seeds indoors Jan 30 – Feb 13 and set transplants outside Apr 3 – Apr 17, once nights stay above 50°F and the soil is near 60°F. That leaves 227 days between the 30% frost dates, enough for most varieties including 80–85-day slicers. More: tomato planting dates by zone.
How long is the growing season in Gresham?
About 250 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 216 days, and in 1 year in 10 it runs 288 days or more. In fall there is a 10% chance of frost by Oct 30 and a 30% chance by Nov 9. That ranks 2nd longest of 8 Oregon cities on this site.
When should I plant a fall garden in Gresham?
Count back from the first fall frost (Nov 9): transplant broccoli Aug 17 – Aug 31; sow kale Aug 31 – Sep 28; sow lettuce Aug 31 – Sep 28; sow radishes Sep 28 – Oct 26. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Dec 15. How the math works: succession and fall planting.
Did Gresham's hardiness zone change on the 2023 map?
Yes. Most of Gresham was zone 8b on the 2012 map and is zone 9a on the 2023 map — half a zone warmer, like about 56% of U.S. ZIP codes. The shift comes from a newer 1991–2020 averaging period plus more weather stations and better mapping; it does not mean last frost comes earlier. Why the 2023 map is warmer.
Is all of Gresham in zone 9a?
No. Zone 9a covers about 56% of the city's land; the rest is in 8b (44%), measured across the city's 6 ZIP codes. Check your own ZIP code in the table above or with the ZIP lookup.