Frost dates for 98603Ariel, WA
The average last spring frost in Ariel is April 1 and the average first fall frost is November 18, giving a typical growing season of about 227 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 1
- Average first fall frost
- Nov 18
- Growing season
- 227 days
Safer after May 2 (1-in-10 risk)
Possible by Oct 29 (1-in-10 risk)
First frost typically in 19 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 13 · May 2 · May 24 | Oct 9 · Oct 29 · Nov 18 | 177 days | 100% |
| Frost / freeze (32°F) | Mar 6 · Apr 1 · May 2 | Oct 29 · Nov 18 · Dec 8 | 227 days | 100% |
| Hard freeze (28°F) | Jan 9 · Feb 22 · Mar 21 | Nov 12 · Dec 7 · Jan 10 | 286 days | 99% |
Planting calendar for Ariel
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 1 – May 7 |
| Tomatoes | Transplant outdoors | Apr 17 – Jul 29 |
| Peppers | Start seeds indoors | Mar 1 – Apr 1 |
| Peppers | Transplant outdoors | May 1 – Jun 1 |
| Eggplant | Start seeds indoors | Mar 18 – Apr 16 |
| Eggplant | Transplant outdoors | May 1 – Jun 1 |
| Cucumbers | Sow outdoors | May 1 – Aug 8 |
| Summer squash | Sow outdoors | Apr 17 – Jun 1 |
| Winter squash & pumpkins | Sow outdoors | May 1 – Jun 1 |
| Snap beans | Sow outdoors | Apr 17 – Aug 31 |
| Sweet corn | Sow outdoors | Apr 17 – Jul 29 |
| Watermelon & cantaloupe | Sow outdoors | May 1 – Jun 1 |
| Okra | Sow outdoors | Apr 24 – May 17 |
| Peas | Sow outdoors (spring) | Mar 1 – Apr 16 |
| Potatoes | Plant outdoors (spring) | Mar 1 – May 1 |
| Onions | Start seeds indoors (spring) | Jan 18 – Feb 14 |
| Onions | Transplant outdoors (spring) | Mar 18 – Apr 16 |
| Broccoli | Start seeds indoors (spring) | Feb 11 – Mar 17 |
| Broccoli | Transplant outdoors (spring) | Mar 18 – Apr 16 |
| Broccoli | Start seeds indoors (fall) | Jul 19 – Jul 29 |
| Broccoli | Transplant outdoors (fall) | Aug 18 – Aug 29 |
| Cabbage | Start seeds indoors (spring) | Feb 1 – Mar 1 |
| Cabbage | Transplant outdoors (spring) | Mar 1 – Apr 1 |
| Cabbage | Start seeds indoors (fall) | Jul 9 – Aug 8 |
| Cabbage | Transplant outdoors (fall) | Aug 8 – Sep 8 |
| Leaf lettuce | Sow outdoors (spring) | Mar 1 – May 17 |
| Leaf lettuce | Sow outdoors (fall) | Aug 8 – Sep 24 |
| Spinach | Sow outdoors (spring) | Feb 22 – Apr 7 |
| Spinach | Sow outdoors (fall) | Aug 25 – Sep 29 |
| Radishes | Sow outdoors (spring) | Mar 1 – Apr 21 |
| Radishes | Sow outdoors (fall) | Aug 8 – Oct 9 |
| Kale | Sow outdoors (spring) | Mar 18 – Apr 7 |
| Kale | Sow outdoors (fall) | Aug 1 – Sep 8 |
| Carrots | Sow outdoors (spring) | Apr 1 – May 17 |
| Carrots | Sow outdoors (fall) | Jul 9 – Aug 24 |
| Garlic | Plant outdoors (fall) | Nov 8 – Dec 9 |
Where these dates come from
ZIP code 98603 is matched to the NOAA station Cougar 6 E, WA, 21.7 km away, at 659 ft elevation (118 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Cougar 6 E, WA (used) | 659 ft | Apr 1 | Nov 18 |
| Battle Ground, WA | 284 ft | Apr 26 | Oct 16 |
| Saint Helens Rfd, OR | 269 ft | Apr 18 | Nov 7 |
| Vancouver 4 Nne, WA | 210 ft | Apr 26 | Oct 18 |
Frost dates near Ariel
- Amboy, WA 98601 · last Apr 26, first Oct 16
- Cougar, WA 98616 · last Apr 1, first Nov 18
- Yacolt, WA 98675 · last Apr 1, first Nov 18
- La Center, WA 98629 · last Apr 26, first Oct 16
- Heisson, WA 98622 · last Apr 26, first Oct 16
- Woodland, WA 98674 · last Apr 10, first Nov 2
- Battle Ground, WA 98604 · last Apr 26, first Oct 16
- Kalama, WA 98625 · last May 8, first Oct 1
Frequently asked questions
- When is the last frost in Ariel, WA?
- For ZIP code 98603, the average last spring frost (32°F) is April 1, based on NOAA 1991-2020 climate normals for the Cougar 6 E, WA weather station. There is a 1-in-10 chance of a frost after May 2.
- When is the first frost in Ariel, WA?
- The average first fall frost (32°F) is November 18. There is a 1-in-10 chance of frost by October 29, so tender plants are at risk from that point on.
- How long is the growing season in 98603?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 227 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.