Frost dates for 50674Sumner, IA
The average last spring frost in Sumner is April 29 and the average first fall frost is October 9, giving a typical growing season of about 162 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 29
- Average first fall frost
- Oct 9
- Growing season
- 162 days
Safer after May 9 (1-in-10 risk)
Possible by Sep 25 (1-in-10 risk)
Last frost typically in 179 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 24 · May 7 · May 20 | Sep 17 · Sep 30 · Oct 12 | 144 days | 100% |
| Frost / freeze (32°F) | Apr 14 · Apr 29 · May 9 | Sep 25 · Oct 9 · Oct 22 | 162 days | 100% |
| Hard freeze (28°F) | Apr 4 · Apr 18 · May 3 | Oct 5 · Oct 20 · Oct 31 | 184 days | 100% |
Planting calendar for Sumner
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 29 – Jun 4 |
| Tomatoes | Transplant outdoors | May 15 – Jun 19 |
| Peppers | Start seeds indoors | Mar 29 – Apr 29 |
| Peppers | Transplant outdoors | May 29 – Jun 29 |
| Eggplant | Start seeds indoors | Apr 15 – May 14 |
| Eggplant | Transplant outdoors | May 29 – Jun 29 |
| Cucumbers | Sow outdoors | May 29 – Jun 29 |
| Summer squash | Sow outdoors | May 15 – Jun 29 |
| Winter squash & pumpkins | Sow outdoors | May 29 – Jun 29 |
| Snap beans | Sow outdoors | May 15 – Jul 22 |
| Sweet corn | Sow outdoors | May 15 – Jun 19 |
| Watermelon & cantaloupe | Sow outdoors | May 29 – Jun 29 |
| Okra | Sow outdoors | May 22 – Jun 14 |
| Peas | Sow outdoors (spring) | Mar 29 – May 14 |
| Potatoes | Plant outdoors (spring) | Mar 29 – May 29 |
| Onions | Start seeds indoors (spring) | Feb 15 – Mar 14 |
| Onions | Transplant outdoors (spring) | Apr 15 – May 14 |
| Broccoli | Start seeds indoors (spring) | Mar 11 – Apr 14 |
| Broccoli | Transplant outdoors (spring) | Apr 15 – May 14 |
| Broccoli | Start seeds indoors (fall) | Jun 9 – Jun 19 |
| Broccoli | Transplant outdoors (fall) | Jul 9 – Jul 20 |
| Cabbage | Start seeds indoors (spring) | Mar 1 – Mar 29 |
| Cabbage | Transplant outdoors (spring) | Mar 29 – Apr 29 |
| Cabbage | Start seeds indoors (fall) | May 30 – Jun 29 |
| Cabbage | Transplant outdoors (fall) | Jun 29 – Jul 30 |
| Leaf lettuce | Sow outdoors (spring) | Mar 29 – Jun 14 |
| Leaf lettuce | Sow outdoors (fall) | Jun 29 – Aug 15 |
| Spinach | Sow outdoors (spring) | Mar 22 – May 5 |
| Spinach | Sow outdoors (fall) | Jul 16 – Aug 20 |
| Radishes | Sow outdoors (spring) | Mar 29 – May 19 |
| Radishes | Sow outdoors (fall) | Jun 29 – Aug 30 |
| Kale | Sow outdoors (spring) | Apr 15 – May 5 |
| Kale | Sow outdoors (fall) | Jun 22 – Jul 30 |
| Carrots | Sow outdoors (spring) | Apr 29 – Jun 14 |
| Carrots | Sow outdoors (fall) | May 30 – Jul 15 |
| Garlic | Plant outdoors (fall) | Sep 29 – Oct 30 |
Where these dates come from
ZIP code 50674 is matched to the NOAA station Tripoli, IA, 11.8 km away, at 1,055 ft elevation (34 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Tripoli, IA (used) | 1,055 ft | Apr 29 | Oct 9 |
| Fayette, IA | 1,145 ft | May 4 | Oct 4 |
| Oelwein 1E, IA | 1,165 ft | Apr 27 | Oct 13 |
| Oelwein 2 S, IA | 1,010 ft | Apr 30 | Oct 9 |
Frost dates near Sumner
- Westgate, IA 50681 · last Apr 29, first Oct 9
- Tripoli, IA 50676 · last Apr 29, first Oct 9
- Fredericksburg, IA 50630 · last May 2, first Oct 5
- Frederika, IA 50631 · last Apr 29, first Oct 9
- Oran, IA 50664 · last Apr 29, first Oct 9
- Hawkeye, IA 52147 · last May 4, first Oct 4
- Readlyn, IA 50668 · last Apr 29, first Oct 9
- Randalia, IA 52164 · last May 4, first Oct 4
Frequently asked questions
- When is the last frost in Sumner, IA?
- For ZIP code 50674, the average last spring frost (32°F) is April 29, based on NOAA 1991-2020 climate normals for the Tripoli, IA weather station. There is a 1-in-10 chance of a frost after May 9.
- When is the first frost in Sumner, IA?
- The average first fall frost (32°F) is October 9. There is a 1-in-10 chance of frost by September 25, so tender plants are at risk from that point on.
- How long is the growing season in 50674?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 162 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.