Frost dates for 50616Charles City, IA
The average last spring frost in Charles City is April 30 and the average first fall frost is October 6, giving a typical growing season of about 157 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 30
- Average first fall frost
- Oct 6
- Growing season
- 157 days
Safer after May 14 (1-in-10 risk)
Possible by Sep 21 (1-in-10 risk)
Last frost typically in 185 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 27 · May 9 · May 22 | Sep 15 · Sep 27 · Oct 9 | 141 days | 100% |
| Frost / freeze (32°F) | Apr 15 · Apr 30 · May 14 | Sep 21 · Oct 6 · Oct 19 | 157 days | 100% |
| Hard freeze (28°F) | Apr 5 · Apr 21 · May 6 | Oct 3 · Oct 17 · Oct 29 | 178 days | 100% |
Planting calendar for Charles City
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 30 – Jun 5 |
| Tomatoes | Transplant outdoors | May 16 – Jun 16 |
| Peppers | Start seeds indoors | Mar 30 – Apr 30 |
| Peppers | Transplant outdoors | May 30 – Jun 30 |
| Eggplant | Start seeds indoors | Apr 16 – May 15 |
| Eggplant | Transplant outdoors | May 30 – Jun 30 |
| Cucumbers | Sow outdoors | May 30 – Jun 26 |
| Summer squash | Sow outdoors | May 16 – Jun 30 |
| Winter squash & pumpkins | Sow outdoors | May 30 – Jun 30 |
| Snap beans | Sow outdoors | May 16 – Jul 19 |
| Sweet corn | Sow outdoors | May 16 – Jun 16 |
| Watermelon & cantaloupe | Sow outdoors | May 30 – Jun 30 |
| Okra | Sow outdoors | May 23 – Jun 15 |
| Peas | Sow outdoors (spring) | Mar 30 – May 15 |
| Potatoes | Plant outdoors (spring) | Mar 30 – May 30 |
| Onions | Start seeds indoors (spring) | Feb 16 – Mar 15 |
| Onions | Transplant outdoors (spring) | Apr 16 – May 15 |
| Broccoli | Start seeds indoors (spring) | Mar 12 – Apr 15 |
| Broccoli | Transplant outdoors (spring) | Apr 16 – May 15 |
| Broccoli | Start seeds indoors (fall) | Jun 6 – Jun 16 |
| Broccoli | Transplant outdoors (fall) | Jul 6 – Jul 17 |
| Cabbage | Start seeds indoors (spring) | Mar 2 – Mar 30 |
| Cabbage | Transplant outdoors (spring) | Mar 30 – Apr 30 |
| Cabbage | Start seeds indoors (fall) | May 27 – Jun 26 |
| Cabbage | Transplant outdoors (fall) | Jun 26 – Jul 27 |
| Leaf lettuce | Sow outdoors (spring) | Mar 30 – Jun 15 |
| Leaf lettuce | Sow outdoors (fall) | Jun 26 – Aug 12 |
| Spinach | Sow outdoors (spring) | Mar 23 – May 6 |
| Spinach | Sow outdoors (fall) | Jul 13 – Aug 17 |
| Radishes | Sow outdoors (spring) | Mar 30 – May 20 |
| Radishes | Sow outdoors (fall) | Jun 26 – Aug 27 |
| Kale | Sow outdoors (spring) | Apr 16 – May 6 |
| Kale | Sow outdoors (fall) | Jun 19 – Jul 27 |
| Carrots | Sow outdoors (spring) | Apr 30 – Jun 15 |
| Carrots | Sow outdoors (fall) | May 27 – Jul 12 |
| Garlic | Plant outdoors (fall) | Sep 26 – Oct 27 |
Where these dates come from
ZIP code 50616 is matched to the NOAA station Charles City, IA, 1 km away, at 993 ft elevation (11 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Charles City, IA (used) | 993 ft | Apr 30 | Oct 6 |
| Osage, IA | 1,170 ft | Apr 30 | Oct 9 |
| New Hampton, IA | 1,148 ft | May 2 | Oct 5 |
| Allison, IA | 1,038 ft | Apr 27 | Oct 8 |
Frost dates near Charles City
- Floyd, IA 50435 · last Apr 30, first Oct 6
- Colwell, IA 50620 · last Apr 30, first Oct 6
- Ionia, IA 50645 · last May 2, first Oct 5
- Nashua, IA 50658 · last Apr 30, first Oct 6
- Orchard, IA 50460 · last Apr 30, first Oct 9
- Rudd, IA 50471 · last Apr 30, first Oct 9
- Marble Rock, IA 50653 · last Apr 30, first Oct 6
- Greene, IA 50636 · last Apr 27, first Oct 8
Frequently asked questions
- When is the last frost in Charles City, IA?
- For ZIP code 50616, the average last spring frost (32°F) is April 30, based on NOAA 1991-2020 climate normals for the Charles City, IA weather station. There is a 1-in-10 chance of a frost after May 14.
- When is the first frost in Charles City, IA?
- The average first fall frost (32°F) is October 6. There is a 1-in-10 chance of frost by September 21, so tender plants are at risk from that point on.
- How long is the growing season in 50616?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 157 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.