Frost dates for 50170Monroe, IA
The average last spring frost in Monroe is April 21 and the average first fall frost is October 15, giving a typical growing season of about 174 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 21
- Average first fall frost
- Oct 15
- Growing season
- 174 days
Safer after May 5 (1-in-10 risk)
Possible by Sep 30 (1-in-10 risk)
Last frost typically in 169 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 18 · May 2 · May 15 | Sep 19 · Oct 3 · Oct 17 | 154 days | 100% |
| Frost / freeze (32°F) | Apr 7 · Apr 21 · May 5 | Sep 30 · Oct 15 · Oct 27 | 174 days | 100% |
| Hard freeze (28°F) | Mar 29 · Apr 10 · Apr 26 | Oct 13 · Oct 25 · Nov 6 | 196 days | 100% |
Planting calendar for Monroe
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 21 – May 27 |
| Tomatoes | Transplant outdoors | May 7 – Jun 25 |
| Peppers | Start seeds indoors | Mar 21 – Apr 21 |
| Peppers | Transplant outdoors | May 21 – Jun 21 |
| Eggplant | Start seeds indoors | Apr 7 – May 6 |
| Eggplant | Transplant outdoors | May 21 – Jun 21 |
| Cucumbers | Sow outdoors | May 21 – Jul 5 |
| Summer squash | Sow outdoors | May 7 – Jun 21 |
| Winter squash & pumpkins | Sow outdoors | May 21 – Jun 21 |
| Snap beans | Sow outdoors | May 7 – Jul 28 |
| Sweet corn | Sow outdoors | May 7 – Jun 25 |
| Watermelon & cantaloupe | Sow outdoors | May 21 – Jun 21 |
| Okra | Sow outdoors | May 14 – Jun 6 |
| Peas | Sow outdoors (spring) | Mar 21 – May 6 |
| Potatoes | Plant outdoors (spring) | Mar 21 – May 21 |
| Onions | Start seeds indoors (spring) | Feb 7 – Mar 6 |
| Onions | Transplant outdoors (spring) | Apr 7 – May 6 |
| Broccoli | Start seeds indoors (spring) | Mar 3 – Apr 6 |
| Broccoli | Transplant outdoors (spring) | Apr 7 – May 6 |
| Broccoli | Start seeds indoors (fall) | Jun 15 – Jun 25 |
| Broccoli | Transplant outdoors (fall) | Jul 15 – Jul 26 |
| Cabbage | Start seeds indoors (spring) | Feb 21 – Mar 21 |
| Cabbage | Transplant outdoors (spring) | Mar 21 – Apr 21 |
| Cabbage | Start seeds indoors (fall) | Jun 5 – Jul 5 |
| Cabbage | Transplant outdoors (fall) | Jul 5 – Aug 5 |
| Leaf lettuce | Sow outdoors (spring) | Mar 21 – Jun 6 |
| Leaf lettuce | Sow outdoors (fall) | Jul 5 – Aug 21 |
| Spinach | Sow outdoors (spring) | Mar 14 – Apr 27 |
| Spinach | Sow outdoors (fall) | Jul 22 – Aug 26 |
| Radishes | Sow outdoors (spring) | Mar 21 – May 11 |
| Radishes | Sow outdoors (fall) | Jul 5 – Sep 5 |
| Kale | Sow outdoors (spring) | Apr 7 – Apr 27 |
| Kale | Sow outdoors (fall) | Jun 28 – Aug 5 |
| Carrots | Sow outdoors (spring) | Apr 21 – Jun 6 |
| Carrots | Sow outdoors (fall) | Jun 5 – Jul 21 |
| Garlic | Plant outdoors (fall) | Oct 5 – Nov 5 |
Where these dates come from
ZIP code 50170 is matched to the NOAA station Des Moines 17 E, IA, 15.7 km away, at 921 ft elevation (1 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Des Moines 17 E, IA (used) | 921 ft | Apr 21 | Oct 15 |
| Newton, IA | 960 ft | Apr 22 | Oct 17 |
| Knoxville, IA | 895 ft | Apr 20 | Oct 19 |
| Grinnell 3 Sw, IA | 905 ft | May 3 | Oct 6 |
Frost dates near Monroe
- Reasnor, IA 50232 · last Apr 22, first Oct 17
- Otley, IA 50214 · last Apr 20, first Oct 19
- Prairie City, IA 50228 · last Apr 21, first Oct 15
- Swan, IA 50252 · last Apr 21, first Oct 15
- Killduff, IA 50137 · last Apr 22, first Oct 17
- Pella, IA 50219 · last Apr 20, first Oct 19
- Newton, IA 50208 · last Apr 22, first Oct 17
- Pleasantville, IA 50225 · last Apr 20, first Oct 19
Frequently asked questions
- When is the last frost in Monroe, IA?
- For ZIP code 50170, the average last spring frost (32°F) is April 21, based on NOAA 1991-2020 climate normals for the Des Moines 17 E, IA weather station. There is a 1-in-10 chance of a frost after May 5.
- When is the first frost in Monroe, IA?
- The average first fall frost (32°F) is October 15. There is a 1-in-10 chance of frost by September 30, so tender plants are at risk from that point on.
- How long is the growing season in 50170?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 174 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.