Frost dates for 97342Detroit, OR
The average last spring frost in Detroit is March 9 and the average first fall frost is December 3, giving a typical growing season of about 270 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Mar 9
- Average first fall frost
- Dec 3
- Growing season
- 270 days
Safer after Apr 8 (1-in-10 risk)
Possible by Nov 8 (1-in-10 risk)
First frost typically in 32 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) | Mar 26 · Apr 17 · May 12 | Oct 25 · Nov 11 · Dec 2 | 207 days | 100% |
| Frost / freeze (32°F) | Feb 2 · Mar 9 · Apr 8 | Nov 8 · Dec 3 · Jan 4 | 270 days | 100% |
| Hard freeze (28°F) | Dec 23 · Feb 5 · Mar 8 | Nov 22 · Dec 26 · Feb 5 | 327 days | 84% |
Planting calendar for Detroit
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 | Feb 6 – Apr 14 |
| Tomatoes | Transplant outdoors | Mar 25 – Aug 13 |
| Peppers | Start seeds indoors | Feb 6 – Mar 9 |
| Peppers | Transplant outdoors | Apr 8 – May 9 |
| Eggplant | Start seeds indoors | Feb 23 – Mar 24 |
| Eggplant | Transplant outdoors | Apr 8 – May 9 |
| Cucumbers | Sow outdoors | Apr 8 – Aug 23 |
| Summer squash | Sow outdoors | Mar 25 – May 9 |
| Winter squash & pumpkins | Sow outdoors | Apr 8 – May 9 |
| Snap beans | Sow outdoors | Mar 25 – Sep 15 |
| Sweet corn | Sow outdoors | Mar 25 – Aug 13 |
| Watermelon & cantaloupe | Sow outdoors | Apr 8 – May 9 |
| Okra | Sow outdoors | Apr 1 – Apr 24 |
| Peas | Sow outdoors (spring) | Feb 6 – Mar 24 |
| Potatoes | Plant outdoors (spring) | Feb 6 – Apr 8 |
| Onions | Start seeds indoors (spring) | Dec 26 – Jan 22 |
| Onions | Transplant outdoors (spring) | Feb 23 – Mar 24 |
| Broccoli | Start seeds indoors (spring) | Jan 19 – Feb 22 |
| Broccoli | Transplant outdoors (spring) | Feb 23 – Mar 24 |
| Broccoli | Start seeds indoors (fall) | Aug 3 – Aug 13 |
| Broccoli | Transplant outdoors (fall) | Sep 2 – Sep 13 |
| Cabbage | Start seeds indoors (spring) | Jan 9 – Feb 6 |
| Cabbage | Transplant outdoors (spring) | Feb 6 – Mar 9 |
| Cabbage | Start seeds indoors (fall) | Jul 24 – Aug 23 |
| Cabbage | Transplant outdoors (fall) | Aug 23 – Sep 23 |
| Leaf lettuce | Sow outdoors (spring) | Feb 6 – Apr 24 |
| Leaf lettuce | Sow outdoors (fall) | Aug 23 – Oct 9 |
| Spinach | Sow outdoors (spring) | Jan 30 – Mar 15 |
| Spinach | Sow outdoors (fall) | Sep 9 – Oct 14 |
| Radishes | Sow outdoors (spring) | Feb 6 – Mar 29 |
| Radishes | Sow outdoors (fall) | Aug 23 – Oct 24 |
| Kale | Sow outdoors (spring) | Feb 23 – Mar 15 |
| Kale | Sow outdoors (fall) | Aug 16 – Sep 23 |
| Carrots | Sow outdoors (spring) | Mar 9 – Apr 24 |
| Carrots | Sow outdoors (fall) | Jul 24 – Sep 8 |
| Garlic | Plant outdoors (fall) | Nov 23 – Dec 24 |
Where these dates come from
ZIP code 97342 is matched to the NOAA station Detroit Dam, OR, 8.4 km away, at 1,220 ft elevation (381 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Detroit Dam, OR (used) | 1,220 ft | Mar 9 | Dec 3 |
| Marion Forks Fish Hatchery, OR | 2,475 ft | May 15 | Sep 30 |
| Santiam Junction, OR | 3,750 ft | — | — |
| Scotts Mills 9 Se, OR | 2,315 ft | Apr 27 | Nov 4 |
Frost dates near Detroit
- Idanha, OR 97350 · last Mar 9, first Dec 3
- Gates, OR 97346 · last Mar 9, first Dec 3
- Mill City, OR 97360 · last Mar 9, first Dec 3
- Lyons, OR 97358 · last Apr 30, first Oct 22
- Saint Benedict, OR 97373 · last Apr 27, first Nov 4
- Mehama, OR 97384 · last Mar 29, first Nov 6
- Cascadia, OR 97329 · last Apr 29, first Oct 13
- Scotts Mills, OR 97375 · last Apr 30, first Oct 22
Frequently asked questions
- When is the last frost in Detroit, OR?
- For ZIP code 97342, the average last spring frost (32°F) is March 9, based on NOAA 1991-2020 climate normals for the Detroit Dam, OR weather station. There is a 1-in-10 chance of a frost after April 8.
- When is the first frost in Detroit, OR?
- The average first fall frost (32°F) is December 3. There is a 1-in-10 chance of frost by November 8, so tender plants are at risk from that point on.
- How long is the growing season in 97342?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 270 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.