Frost Dates for Happy Valley, OR
In Happy Valley, OR, the average last spring frost is around Mar 18 and the average first fall frost around Nov 18, for a growing season of about 244 days. For frost-tender plants, wait until Apr 11, when the chance of frost drops to 10%.
Based on NOAA 1991–2020 records from the Oregon City, OR weather station, 7 miles away, elevation 167 ft. Frost can come earlier in low spots and valleys and later near cities and large lakes.
Frost probability by date
Chance of a 32°F frost after the spring date, or before the fall date.
| Chance | Last spring frost | First fall frost |
|---|---|---|
| 10% | Apr 11 | Oct 30 |
| 20% | Apr 1 | Nov 4 |
| 30% | Mar 27 | Nov 9 |
| 40% | Mar 23 | Nov 13 |
| 50% | Mar 18 | Nov 18 |
| 60% | Mar 12 | Nov 22 |
| 70% | Mar 5 | Nov 28 |
| 80% | Feb 27 | Dec 3 |
| 90% | Feb 19 | Dec 12 |
Light frost vs. hard freeze
Average (50%) dates for each temperature. Tender plants are damaged at 36°F; most hardy crops survive until 28°F.
| Temperature | Last in spring | First in fall |
|---|---|---|
| Light frost (36°F) | Apr 15 | Oct 31 |
| Frost / freeze (32°F) | Mar 18 | Nov 18 |
| Hard freeze (28°F) | Feb 12 | Dec 8 |
Planting calendar for Happy Valley
Transplant Mar 25 – Apr 8
Transplant Apr 1 – Apr 15
Transplant Apr 1 – Apr 15
Transplant Mar 25 – Apr 8
Sow or transplant Mar 25 – Apr 8
Sow or transplant Mar 25 – Apr 8
Sow or transplant Apr 1 – Apr 15
Sow or transplant Feb 18 – Mar 4
Fall sowing Sep 23 – Oct 21
Fall sowing Sep 23 – Oct 14
Fall sowing Sep 9 – Sep 23
Sow or transplant Feb 18 – Mar 4
Fall sowing Sep 9 – Oct 7
Transplant Mar 4 – Mar 18
Fall sowing Aug 26 – Sep 9
Transplant Feb 25 – Mar 11
Fall sowing Aug 26 – Sep 9
Fall sowing Aug 26 – Sep 9
Fall sowing Oct 7 – Oct 28
Fall sowing Sep 9 – Sep 23
Plant Feb 18 – Mar 4
Based on the average last frost (Mar 18) and first frost (Nov 18). The dashed lines mark those dates. Seed packets list days to maturity; adjust for your varieties.