Frost dates for 50661North Washington, IA
The average last spring frost in North Washington is May 2 and the average first fall frost is October 5, giving a typical growing season of about 155 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 2
- Average first fall frost
- Oct 5
- Growing season
- 155 days
Safer after May 14 (1-in-10 risk)
Possible by Sep 23 (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) | Apr 29 · May 10 · May 23 | Sep 16 · Sep 28 · Oct 9 | 139 days | 100% |
| Frost / freeze (32°F) | Apr 17 · May 2 · May 14 | Sep 23 · Oct 5 · Oct 18 | 155 days | 100% |
| Hard freeze (28°F) | Apr 5 · Apr 20 · May 5 | Oct 1 · Oct 15 · Oct 27 | 175 days | 100% |
Planting calendar for North Washington
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 1 – Jun 7 |
| Tomatoes | Transplant outdoors | May 18 – Jun 15 |
| Peppers | Start seeds indoors | Apr 1 – May 2 |
| Peppers | Transplant outdoors | Jun 1 – Jul 2 |
| Eggplant | Start seeds indoors | Apr 18 – May 17 |
| Eggplant | Transplant outdoors | Jun 1 – Jul 2 |
| Cucumbers | Sow outdoors | Jun 1 – Jun 25 |
| Summer squash | Sow outdoors | May 18 – Jul 2 |
| Winter squash & pumpkins | Sow outdoors | Jun 1 – Jul 2 |
| Snap beans | Sow outdoors | May 18 – Jul 18 |
| Sweet corn | Sow outdoors | May 18 – Jun 15 |
| Watermelon & cantaloupe | Sow outdoors | Jun 1 – Jul 2 |
| Okra | Sow outdoors | May 25 – Jun 17 |
| Peas | Sow outdoors (spring) | Apr 1 – May 17 |
| Potatoes | Plant outdoors (spring) | Apr 1 – Jun 1 |
| Onions | Start seeds indoors (spring) | Feb 18 – Mar 17 |
| Onions | Transplant outdoors (spring) | Apr 18 – May 17 |
| Broccoli | Start seeds indoors (spring) | Mar 14 – Apr 17 |
| Broccoli | Transplant outdoors (spring) | Apr 18 – May 17 |
| Broccoli | Start seeds indoors (fall) | Jun 5 – Jun 15 |
| Broccoli | Transplant outdoors (fall) | Jul 5 – Jul 16 |
| Cabbage | Start seeds indoors (spring) | Mar 4 – Apr 1 |
| Cabbage | Transplant outdoors (spring) | Apr 1 – May 2 |
| Cabbage | Start seeds indoors (fall) | May 26 – Jun 25 |
| Cabbage | Transplant outdoors (fall) | Jun 25 – Jul 26 |
| Leaf lettuce | Sow outdoors (spring) | Apr 1 – Jun 17 |
| Leaf lettuce | Sow outdoors (fall) | Jun 25 – Aug 11 |
| Spinach | Sow outdoors (spring) | Mar 25 – May 8 |
| Spinach | Sow outdoors (fall) | Jul 12 – Aug 16 |
| Radishes | Sow outdoors (spring) | Apr 1 – May 22 |
| Radishes | Sow outdoors (fall) | Jun 25 – Aug 26 |
| Kale | Sow outdoors (spring) | Apr 18 – May 8 |
| Kale | Sow outdoors (fall) | Jun 18 – Jul 26 |
| Carrots | Sow outdoors (spring) | May 2 – Jun 17 |
| Carrots | Sow outdoors (fall) | May 26 – Jul 11 |
| Garlic | Plant outdoors (fall) | Sep 25 – Oct 26 |
Where these dates come from
ZIP code 50661 is matched to the NOAA station New Hampton, IA, 11.5 km away, at 1,148 ft elevation (3 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| New Hampton, IA (used) | 1,148 ft | May 2 | Oct 5 |
| Charles City, IA | 993 ft | Apr 30 | Oct 6 |
| Tripoli, IA | 1,055 ft | Apr 29 | Oct 9 |
| Osage, IA | 1,170 ft | Apr 30 | Oct 9 |
Frost dates near North Washington
- Alta Vista, IA 50603 · last May 2, first Oct 5
- Ionia, IA 50645 · last May 2, first Oct 5
- New Hampton, IA 50659 · last May 2, first Oct 5
- Colwell, IA 50620 · last Apr 30, first Oct 6
- Elma, IA 50628 · last May 8, first Oct 1
- Nashua, IA 50658 · last Apr 30, first Oct 6
- Charles City, IA 50616 · last Apr 30, first Oct 6
- Lawler, IA 52154 · last May 2, first Oct 5
Frequently asked questions
- When is the last frost in North Washington, IA?
- For ZIP code 50661, the average last spring frost (32°F) is May 2, based on NOAA 1991-2020 climate normals for the New Hampton, IA weather station. There is a 1-in-10 chance of a frost after May 14.
- When is the first frost in North Washington, IA?
- The average first fall frost (32°F) is October 5. There is a 1-in-10 chance of frost by September 23, so tender plants are at risk from that point on.
- How long is the growing season in 50661?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 155 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.