Frost dates for 99337Kennewick, WA
The average last spring frost in Kennewick is March 28 and the average first fall frost is October 30, giving a typical growing season of about 216 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Mar 28
- Average first fall frost
- Oct 30
- Growing season
- 216 days
Safer after Apr 10 (1-in-10 risk)
Possible by Oct 18 (1-in-10 risk)
Last frost typically in 146 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 30 · Apr 14 · Apr 30 | Oct 7 · Oct 21 · Nov 2 | 189 days | 100% |
| Frost / freeze (32°F) | Mar 9 · Mar 28 · Apr 10 | Oct 18 · Oct 30 · Nov 15 | 216 days | 100% |
| Hard freeze (28°F) | Feb 20 · Mar 8 · Mar 29 | Oct 27 · Nov 11 · Dec 1 | 246 days | 100% |
Planting calendar for Kennewick
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 25 – May 3 |
| Tomatoes | Transplant outdoors | Apr 13 – Jul 10 |
| Peppers | Start seeds indoors | Feb 25 – Mar 28 |
| Peppers | Transplant outdoors | Apr 27 – May 28 |
| Eggplant | Start seeds indoors | Mar 14 – Apr 12 |
| Eggplant | Transplant outdoors | Apr 27 – May 28 |
| Cucumbers | Sow outdoors | Apr 27 – Jul 20 |
| Summer squash | Sow outdoors | Apr 13 – May 28 |
| Winter squash & pumpkins | Sow outdoors | Apr 27 – May 28 |
| Snap beans | Sow outdoors | Apr 13 – Aug 12 |
| Sweet corn | Sow outdoors | Apr 13 – Jul 10 |
| Watermelon & cantaloupe | Sow outdoors | Apr 27 – May 28 |
| Okra | Sow outdoors | Apr 20 – May 13 |
| Peas | Sow outdoors (spring) | Feb 25 – Apr 12 |
| Potatoes | Plant outdoors (spring) | Feb 25 – Apr 27 |
| Onions | Start seeds indoors (spring) | Jan 14 – Feb 10 |
| Onions | Transplant outdoors (spring) | Mar 14 – Apr 12 |
| Broccoli | Start seeds indoors (spring) | Feb 7 – Mar 13 |
| Broccoli | Transplant outdoors (spring) | Mar 14 – Apr 12 |
| Broccoli | Start seeds indoors (fall) | Jun 30 – Jul 10 |
| Broccoli | Transplant outdoors (fall) | Jul 30 – Aug 10 |
| Cabbage | Start seeds indoors (spring) | Jan 28 – Feb 25 |
| Cabbage | Transplant outdoors (spring) | Feb 25 – Mar 28 |
| Cabbage | Start seeds indoors (fall) | Jun 20 – Jul 20 |
| Cabbage | Transplant outdoors (fall) | Jul 20 – Aug 20 |
| Leaf lettuce | Sow outdoors (spring) | Feb 25 – May 13 |
| Leaf lettuce | Sow outdoors (fall) | Jul 20 – Sep 5 |
| Spinach | Sow outdoors (spring) | Feb 18 – Apr 3 |
| Spinach | Sow outdoors (fall) | Aug 6 – Sep 10 |
| Radishes | Sow outdoors (spring) | Feb 25 – Apr 17 |
| Radishes | Sow outdoors (fall) | Jul 20 – Sep 20 |
| Kale | Sow outdoors (spring) | Mar 14 – Apr 3 |
| Kale | Sow outdoors (fall) | Jul 13 – Aug 20 |
| Carrots | Sow outdoors (spring) | Mar 28 – May 13 |
| Carrots | Sow outdoors (fall) | Jun 20 – Aug 5 |
| Garlic | Plant outdoors (fall) | Oct 20 – Nov 20 |
Where these dates come from
ZIP code 99337 is matched to the NOAA station Kennewick, WA, 4.4 km away, at 390 ft elevation (148 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Kennewick, WA (used) | 390 ft | Mar 28 | Oct 30 |
| Pasco Tri Cities Ap, WA | 407 ft | Apr 27 | Oct 11 |
| Richland, WA | 373 ft | Apr 6 | Oct 24 |
| Ice Harbor Dam, WA | 368 ft | Apr 7 | Oct 22 |
Frost dates near Kennewick
- Kennewick, WA 99336 · last Mar 28, first Oct 30
- Pasco, WA 99302 · last Mar 28, first Oct 30
- Richland, WA 99352 · last Apr 6, first Oct 24
- Burbank, WA 99323 · last Apr 7, first Oct 22
- Wallula, WA 99363 · last Apr 7, first Oct 22
- West Richland, WA 99353 · last Apr 6, first Oct 24
- Benton City, WA 99320 · last Apr 6, first Oct 24
- Eltopia, WA 99330 · last Apr 21, first Oct 22
Frequently asked questions
- When is the last frost in Kennewick, WA?
- For ZIP code 99337, the average last spring frost (32°F) is March 28, based on NOAA 1991-2020 climate normals for the Kennewick, WA weather station. There is a 1-in-10 chance of a frost after April 10.
- When is the first frost in Kennewick, WA?
- The average first fall frost (32°F) is October 30. There is a 1-in-10 chance of frost by October 18, so tender plants are at risk from that point on.
- How long is the growing season in 99337?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 216 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.