Frost dates for 98850Rock Island, WA
The average last spring frost in Rock Island is April 4 and the average first fall frost is October 28, giving a typical growing season of about 208 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 4
- Average first fall frost
- Oct 28
- Growing season
- 208 days
Safer after Apr 19 (1-in-10 risk)
Possible by Oct 17 (1-in-10 risk)
First frost typically in 3 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 7 · Apr 21 · May 5 | Oct 6 · Oct 17 · Oct 29 | 179 days | 100% |
| Frost / freeze (32°F) | Mar 17 · Apr 4 · Apr 19 | Oct 17 · Oct 28 · Nov 11 | 208 days | 100% |
| Hard freeze (28°F) | Mar 1 · Mar 13 · Apr 2 | Oct 26 · Nov 10 · Nov 25 | 239 days | 100% |
Planting calendar for Rock Island
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 4 – May 10 |
| Tomatoes | Transplant outdoors | Apr 20 – Jul 8 |
| Peppers | Start seeds indoors | Mar 4 – Apr 4 |
| Peppers | Transplant outdoors | May 4 – Jun 4 |
| Eggplant | Start seeds indoors | Mar 21 – Apr 19 |
| Eggplant | Transplant outdoors | May 4 – Jun 4 |
| Cucumbers | Sow outdoors | May 4 – Jul 18 |
| Summer squash | Sow outdoors | Apr 20 – Jun 4 |
| Winter squash & pumpkins | Sow outdoors | May 4 – Jun 4 |
| Snap beans | Sow outdoors | Apr 20 – Aug 10 |
| Sweet corn | Sow outdoors | Apr 20 – Jul 8 |
| Watermelon & cantaloupe | Sow outdoors | May 4 – Jun 4 |
| Okra | Sow outdoors | Apr 27 – May 20 |
| Peas | Sow outdoors (spring) | Mar 4 – Apr 19 |
| Potatoes | Plant outdoors (spring) | Mar 4 – May 4 |
| Onions | Start seeds indoors (spring) | Jan 21 – Feb 17 |
| Onions | Transplant outdoors (spring) | Mar 21 – Apr 19 |
| Broccoli | Start seeds indoors (spring) | Feb 14 – Mar 20 |
| Broccoli | Transplant outdoors (spring) | Mar 21 – Apr 19 |
| Broccoli | Start seeds indoors (fall) | Jun 28 – Jul 8 |
| Broccoli | Transplant outdoors (fall) | Jul 28 – Aug 8 |
| Cabbage | Start seeds indoors (spring) | Feb 4 – Mar 4 |
| Cabbage | Transplant outdoors (spring) | Mar 4 – Apr 4 |
| Cabbage | Start seeds indoors (fall) | Jun 18 – Jul 18 |
| Cabbage | Transplant outdoors (fall) | Jul 18 – Aug 18 |
| Leaf lettuce | Sow outdoors (spring) | Mar 4 – May 20 |
| Leaf lettuce | Sow outdoors (fall) | Jul 18 – Sep 3 |
| Spinach | Sow outdoors (spring) | Feb 25 – Apr 10 |
| Spinach | Sow outdoors (fall) | Aug 4 – Sep 8 |
| Radishes | Sow outdoors (spring) | Mar 4 – Apr 24 |
| Radishes | Sow outdoors (fall) | Jul 18 – Sep 18 |
| Kale | Sow outdoors (spring) | Mar 21 – Apr 10 |
| Kale | Sow outdoors (fall) | Jul 11 – Aug 18 |
| Carrots | Sow outdoors (spring) | Apr 4 – May 20 |
| Carrots | Sow outdoors (fall) | Jun 18 – Aug 3 |
| Garlic | Plant outdoors (fall) | Oct 18 – Nov 18 |
Where these dates come from
ZIP code 98850 is matched to the NOAA station Wenatchee, WA, 14.5 km away, at 626 ft elevation (20 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Wenatchee, WA (used) | 626 ft | Apr 4 | Oct 28 |
| Wenatchee Pangborn Ap, WA | 1,229 ft | Apr 8 | Oct 24 |
| Quincy, WA | 1,286 ft | Apr 21 | Oct 16 |
| Waterville, WA | 2,664 ft | May 14 | Oct 1 |
Frost dates near Rock Island
- Malaga, WA 98828 · last Apr 8, first Oct 24
- East Wenatchee, WA 98802 · last Apr 4, first Oct 28
- Wenatchee, WA 98807 · last Apr 4, first Oct 28
- Palisades, WA 98845 · last Apr 8, first Oct 24
- Monitor, WA 98836 · last Apr 4, first Oct 28
- Quincy, WA 98848 · last Apr 21, first Oct 16
- Waterville, WA 98858 · last May 14, first Oct 1
- Cashmere, WA 98815 · last May 10, first Sep 30
Frequently asked questions
- When is the last frost in Rock Island, WA?
- For ZIP code 98850, the average last spring frost (32°F) is April 4, based on NOAA 1991-2020 climate normals for the Wenatchee, WA weather station. There is a 1-in-10 chance of a frost after April 19.
- When is the first frost in Rock Island, WA?
- The average first fall frost (32°F) is October 28. There is a 1-in-10 chance of frost by October 17, so tender plants are at risk from that point on.
- How long is the growing season in 98850?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 208 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.