Frost dates for 97844Irrigon, OR
The average last spring frost in Irrigon is April 14 and the average first fall frost is October 21, giving a typical growing season of about 188 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 14
- Average first fall frost
- Oct 21
- Growing season
- 188 days
Safer after May 2 (1-in-10 risk)
Possible by Oct 5 (1-in-10 risk)
Last frost typically in 164 days
Frost risk by date
NOAA reports frost dates as probabilities. The middle date is the average (a 50% chance). For spring, the 10% date is a safer planting date: frost after it happens in about 1 year in 10. Light frost (36°F) can damage tender plants; a hard freeze (28°F) kills most annuals.
| Temperature | Last spring: 90% / 50% / 10% chance | First fall: 10% / 50% / 90% chance | Growing season (50%) | Years with at least one |
|---|---|---|---|---|
| Light frost (36°F) | Apr 15 · May 1 · May 13 | Sep 27 · Oct 8 · Oct 22 | 161 days | 100% |
| Frost / freeze (32°F) | Mar 28 · Apr 14 · May 2 | Oct 5 · Oct 21 · Nov 4 | 188 days | 100% |
| Hard freeze (28°F) | Mar 9 · Mar 28 · Apr 15 | Oct 17 · Nov 1 · Nov 19 | 218 days | 100% |
Planting calendar for Irrigon
Planting windows from the University of Maryland Extension calendar, shifted to your average frost dates. Use them as a starting point and adjust for seed packet instructions and local conditions.
| Crop | Task | Window |
|---|---|---|
| Tomatoes | Start seeds indoors | Mar 14 – May 20 |
| Tomatoes | Transplant outdoors | Apr 30 – Jul 1 |
| Peppers | Start seeds indoors | Mar 14 – Apr 14 |
| Peppers | Transplant outdoors | May 14 – Jun 14 |
| Eggplant | Start seeds indoors | Mar 31 – Apr 29 |
| Eggplant | Transplant outdoors | May 14 – Jun 14 |
| Cucumbers | Sow outdoors | May 14 – Jul 11 |
| Summer squash | Sow outdoors | Apr 30 – Jun 14 |
| Winter squash & pumpkins | Sow outdoors | May 14 – Jun 14 |
| Snap beans | Sow outdoors | Apr 30 – Aug 3 |
| Sweet corn | Sow outdoors | Apr 30 – Jul 1 |
| Watermelon & cantaloupe | Sow outdoors | May 14 – Jun 14 |
| Okra | Sow outdoors | May 7 – May 30 |
| Peas | Sow outdoors (spring) | Mar 14 – Apr 29 |
| Potatoes | Plant outdoors (spring) | Mar 14 – May 14 |
| Onions | Start seeds indoors (spring) | Jan 31 – Feb 27 |
| Onions | Transplant outdoors (spring) | Mar 31 – Apr 29 |
| Broccoli | Start seeds indoors (spring) | Feb 24 – Mar 30 |
| Broccoli | Transplant outdoors (spring) | Mar 31 – Apr 29 |
| Broccoli | Start seeds indoors (fall) | Jun 21 – Jul 1 |
| Broccoli | Transplant outdoors (fall) | Jul 21 – Aug 1 |
| Cabbage | Start seeds indoors (spring) | Feb 14 – Mar 14 |
| Cabbage | Transplant outdoors (spring) | Mar 14 – Apr 14 |
| Cabbage | Start seeds indoors (fall) | Jun 11 – Jul 11 |
| Cabbage | Transplant outdoors (fall) | Jul 11 – Aug 11 |
| Leaf lettuce | Sow outdoors (spring) | Mar 14 – May 30 |
| Leaf lettuce | Sow outdoors (fall) | Jul 11 – Aug 27 |
| Spinach | Sow outdoors (spring) | Mar 7 – Apr 20 |
| Spinach | Sow outdoors (fall) | Jul 28 – Sep 1 |
| Radishes | Sow outdoors (spring) | Mar 14 – May 4 |
| Radishes | Sow outdoors (fall) | Jul 11 – Sep 11 |
| Kale | Sow outdoors (spring) | Mar 31 – Apr 20 |
| Kale | Sow outdoors (fall) | Jul 4 – Aug 11 |
| Carrots | Sow outdoors (spring) | Apr 14 – May 30 |
| Carrots | Sow outdoors (fall) | Jun 11 – Jul 27 |
| Garlic | Plant outdoors (fall) | Oct 11 – Nov 11 |
Where these dates come from
ZIP code 97844 is matched to the NOAA station Boardman, OR, 15.1 km away, at 280 ft elevation (32 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Boardman, OR (used) | 280 ft | Apr 14 | Oct 21 |
| Hermiston 2 Nw, OR | 460 ft | Apr 27 | Oct 7 |
| Mcnary Dam #2, OR | 361 ft | Mar 30 | Nov 4 |
| Mcnary Dam, WA | 361 ft | Mar 27 | Nov 4 |
Frost dates near Irrigon
- Plymouth, WA 99346 · last Mar 27, first Nov 4
- Umatilla, OR 97882 · last Apr 27, first Oct 7
- Hermiston, OR 97838 · last Apr 27, first Oct 7
- Boardman, OR 97818 · last Apr 14, first Oct 21
- Paterson, WA 99345 · last Apr 14, first Oct 21
- Stanfield, OR 97875 · last Apr 26, first Oct 10
- Echo, OR 97826 · last Apr 26, first Oct 10
- Kennewick, WA 99338 · last Mar 28, first Oct 30
Frequently asked questions
- When is the last frost in Irrigon, OR?
- For ZIP code 97844, the average last spring frost (32°F) is April 14, based on NOAA 1991-2020 climate normals for the Boardman, OR weather station. There is a 1-in-10 chance of a frost after May 2.
- When is the first frost in Irrigon, OR?
- The average first fall frost (32°F) is October 21. There is a 1-in-10 chance of frost by October 5, so tender plants are at risk from that point on.
- How long is the growing season in 97844?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 188 days long.
- Are these frost dates a forecast?
- No. They are 30-year averages and probabilities from NOAA weather station records. Use them to plan, then watch your local forecast before planting tender crops or leaving them uncovered.