Frost dates for 98833Mazama, WA
The average last spring frost in Mazama is May 9 and the average first fall frost is September 29, giving a typical growing season of about 142 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 9
- Average first fall frost
- Sep 29
- Growing season
- 142 days
Safer after May 24 (1-in-10 risk)
Possible by Sep 15 (1-in-10 risk)
Last frost typically in 187 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) | May 9 · May 25 · Jun 10 | Sep 4 · Sep 17 · Sep 29 | 113 days | 100% |
| Frost / freeze (32°F) | Apr 28 · May 9 · May 24 | Sep 15 · Sep 29 · Oct 10 | 142 days | 100% |
| Hard freeze (28°F) | Apr 11 · Apr 25 · May 9 | Sep 29 · Oct 10 · Oct 25 | 170 days | 100% |
Planting calendar for Mazama
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 | Apr 8 – Jun 14 |
| Tomatoes | Transplant outdoors | May 25 – Jun 9 |
| Peppers | Start seeds indoors | Apr 8 – May 9 |
| Peppers | Transplant outdoors | Jun 8 – Jul 9 |
| Eggplant | Start seeds indoors | Apr 25 – May 24 |
| Eggplant | Transplant outdoors | Jun 8 – Jul 9 |
| Cucumbers | Sow outdoors | Jun 8 – Jun 19 |
| Summer squash | Sow outdoors | May 25 – Jul 9 |
| Winter squash & pumpkins | Sow outdoors | Jun 8 – Jul 9 |
| Snap beans | Sow outdoors | May 25 – Jul 12 |
| Sweet corn | Sow outdoors | May 25 – Jun 9 |
| Watermelon & cantaloupe | Sow outdoors | Jun 8 – Jul 9 |
| Okra | Sow outdoors | Jun 1 – Jun 24 |
| Peas | Sow outdoors (spring) | Apr 8 – May 24 |
| Potatoes | Plant outdoors (spring) | Apr 8 – Jun 8 |
| Onions | Start seeds indoors (spring) | Feb 25 – Mar 24 |
| Onions | Transplant outdoors (spring) | Apr 25 – May 24 |
| Broccoli | Start seeds indoors (spring) | Mar 21 – Apr 24 |
| Broccoli | Transplant outdoors (spring) | Apr 25 – May 24 |
| Broccoli | Start seeds indoors (fall) | May 30 – Jun 9 |
| Broccoli | Transplant outdoors (fall) | Jun 29 – Jul 10 |
| Cabbage | Start seeds indoors (spring) | Mar 11 – Apr 8 |
| Cabbage | Transplant outdoors (spring) | Apr 8 – May 9 |
| Cabbage | Start seeds indoors (fall) | May 20 – Jun 19 |
| Cabbage | Transplant outdoors (fall) | Jun 19 – Jul 20 |
| Leaf lettuce | Sow outdoors (spring) | Apr 8 – Jun 24 |
| Leaf lettuce | Sow outdoors (fall) | Jun 19 – Aug 5 |
| Spinach | Sow outdoors (spring) | Apr 1 – May 15 |
| Spinach | Sow outdoors (fall) | Jul 6 – Aug 10 |
| Radishes | Sow outdoors (spring) | Apr 8 – May 29 |
| Radishes | Sow outdoors (fall) | Jun 19 – Aug 20 |
| Kale | Sow outdoors (spring) | Apr 25 – May 15 |
| Kale | Sow outdoors (fall) | Jun 12 – Jul 20 |
| Carrots | Sow outdoors (spring) | May 9 – Jun 24 |
| Carrots | Sow outdoors (fall) | May 20 – Jul 5 |
| Garlic | Plant outdoors (fall) | Sep 19 – Oct 20 |
Where these dates come from
ZIP code 98833 is matched to the NOAA station Mazama, WA, 2.9 km away, at 2,141 ft elevation (1,396 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Mazama, WA (used) | 2,141 ft | May 9 | Sep 29 |
| Winthrop 1 Wsw, WA | 1,749 ft | May 15 | Sep 22 |
| Stehekin 4 Nw, WA | 1,257 ft | Apr 27 | Oct 17 |
| Ross Dam, WA | 1,236 ft | Apr 8 | Nov 10 |
Frost dates near Mazama
- Winthrop, WA 98862 · last May 15, first Sep 22
- Twisp, WA 98856 · last May 15, first Sep 22
- Stehekin, WA 98852 · last Apr 27, first Oct 17
- Carlton, WA 98814 · last Apr 21, first Oct 15
- Conconully, WA 98819 · last May 9, first Sep 29
- Methow, WA 98834 · last May 25, first Sep 19
- Riverside, WA 98849 · last Apr 30, first Oct 7
- Malott, WA 98829 · last Apr 30, first Oct 7
Frequently asked questions
- When is the last frost in Mazama, WA?
- For ZIP code 98833, the average last spring frost (32°F) is May 9, based on NOAA 1991-2020 climate normals for the Mazama, WA weather station. There is a 1-in-10 chance of a frost after May 24.
- When is the first frost in Mazama, WA?
- The average first fall frost (32°F) is September 29. There is a 1-in-10 chance of frost by September 15, so tender plants are at risk from that point on.
- How long is the growing season in 98833?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 142 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.