Frost dates for 98295Sumas, WA
The average last spring frost in Sumas is April 18 and the average first fall frost is October 18, giving a typical growing season of about 185 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 18
- Average first fall frost
- Oct 18
- Growing season
- 185 days
Safer after May 5 (1-in-10 risk)
Possible by Sep 28 (1-in-10 risk)
Last frost typically in 166 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 23 · May 7 · May 22 | Sep 10 · Sep 29 · Oct 14 | 143 days | 100% |
| Frost / freeze (32°F) | Mar 27 · Apr 18 · May 5 | Sep 28 · Oct 18 · Nov 8 | 185 days | 100% |
| Hard freeze (28°F) | Feb 25 · Mar 18 · Apr 8 | Oct 20 · Nov 7 · Dec 4 | 235 days | 100% |
Planting calendar for Sumas
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 18 – May 24 |
| Tomatoes | Transplant outdoors | May 4 – Jun 28 |
| Peppers | Start seeds indoors | Mar 18 – Apr 18 |
| Peppers | Transplant outdoors | May 18 – Jun 18 |
| Eggplant | Start seeds indoors | Apr 4 – May 3 |
| Eggplant | Transplant outdoors | May 18 – Jun 18 |
| Cucumbers | Sow outdoors | May 18 – Jul 8 |
| Summer squash | Sow outdoors | May 4 – Jun 18 |
| Winter squash & pumpkins | Sow outdoors | May 18 – Jun 18 |
| Snap beans | Sow outdoors | May 4 – Jul 31 |
| Sweet corn | Sow outdoors | May 4 – Jun 28 |
| Watermelon & cantaloupe | Sow outdoors | May 18 – Jun 18 |
| Okra | Sow outdoors | May 11 – Jun 3 |
| Peas | Sow outdoors (spring) | Mar 18 – May 3 |
| Potatoes | Plant outdoors (spring) | Mar 18 – May 18 |
| Onions | Start seeds indoors (spring) | Feb 4 – Mar 3 |
| Onions | Transplant outdoors (spring) | Apr 4 – May 3 |
| Broccoli | Start seeds indoors (spring) | Feb 28 – Apr 3 |
| Broccoli | Transplant outdoors (spring) | Apr 4 – May 3 |
| Broccoli | Start seeds indoors (fall) | Jun 18 – Jun 28 |
| Broccoli | Transplant outdoors (fall) | Jul 18 – Jul 29 |
| Cabbage | Start seeds indoors (spring) | Feb 18 – Mar 18 |
| Cabbage | Transplant outdoors (spring) | Mar 18 – Apr 18 |
| Cabbage | Start seeds indoors (fall) | Jun 8 – Jul 8 |
| Cabbage | Transplant outdoors (fall) | Jul 8 – Aug 8 |
| Leaf lettuce | Sow outdoors (spring) | Mar 18 – Jun 3 |
| Leaf lettuce | Sow outdoors (fall) | Jul 8 – Aug 24 |
| Spinach | Sow outdoors (spring) | Mar 11 – Apr 24 |
| Spinach | Sow outdoors (fall) | Jul 25 – Aug 29 |
| Radishes | Sow outdoors (spring) | Mar 18 – May 8 |
| Radishes | Sow outdoors (fall) | Jul 8 – Sep 8 |
| Kale | Sow outdoors (spring) | Apr 4 – Apr 24 |
| Kale | Sow outdoors (fall) | Jul 1 – Aug 8 |
| Carrots | Sow outdoors (spring) | Apr 18 – Jun 3 |
| Carrots | Sow outdoors (fall) | Jun 8 – Jul 24 |
| Garlic | Plant outdoors (fall) | Oct 8 – Nov 8 |
Where these dates come from
ZIP code 98295 is matched to the NOAA station Clearbrook, WA, 8.9 km away, at 64 ft elevation (484 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Clearbrook, WA (used) | 64 ft | Apr 18 | Oct 18 |
| Bellingham Intl Ap, WA | 149 ft | Mar 31 | Oct 30 |
| Bellingham 3 Ssw, WA | 15 ft | Apr 1 | Nov 2 |
| Blaine, WA | 60 ft | Mar 31 | Nov 4 |
Frost dates near Sumas
- Maple Falls, WA 98266 · last Apr 18, first Oct 18
- Nooksack, WA 98276 · last Apr 18, first Oct 18
- Everson, WA 98247 · last Apr 18, first Oct 18
- Lynden, WA 98264 · last Apr 18, first Oct 18
- Deming, WA 98244 · last Apr 24, first Oct 29
- Bellingham, WA 98226 · last Mar 31, first Oct 30
- Custer, WA 98240 · last Mar 31, first Nov 4
- Ferndale, WA 98248 · last Mar 31, first Oct 30
Frequently asked questions
- When is the last frost in Sumas, WA?
- For ZIP code 98295, the average last spring frost (32°F) is April 18, based on NOAA 1991-2020 climate normals for the Clearbrook, WA weather station. There is a 1-in-10 chance of a frost after May 5.
- When is the first frost in Sumas, WA?
- The average first fall frost (32°F) is October 18. There is a 1-in-10 chance of frost by September 28, so tender plants are at risk from that point on.
- How long is the growing season in 98295?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 185 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.