Frost dates for 52309Monmouth, IA
The average last spring frost in Monmouth is April 25 and the average first fall frost is October 14, giving a typical growing season of about 171 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 25
- Average first fall frost
- Oct 14
- Growing season
- 171 days
Safer after May 9 (1-in-10 risk)
Possible by Sep 30 (1-in-10 risk)
Last frost typically in 175 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 20 · May 5 · May 18 | Sep 20 · Oct 3 · Oct 16 | 151 days | 100% |
| Frost / freeze (32°F) | Apr 11 · Apr 25 · May 9 | Sep 30 · Oct 14 · Oct 26 | 171 days | 100% |
| Hard freeze (28°F) | Apr 2 · Apr 14 · May 1 | Oct 10 · Oct 24 · Nov 4 | 191 days | 100% |
Planting calendar for Monmouth
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 25 – May 31 |
| Tomatoes | Transplant outdoors | May 11 – Jun 24 |
| Peppers | Start seeds indoors | Mar 25 – Apr 25 |
| Peppers | Transplant outdoors | May 25 – Jun 25 |
| Eggplant | Start seeds indoors | Apr 11 – May 10 |
| Eggplant | Transplant outdoors | May 25 – Jun 25 |
| Cucumbers | Sow outdoors | May 25 – Jul 4 |
| Summer squash | Sow outdoors | May 11 – Jun 25 |
| Winter squash & pumpkins | Sow outdoors | May 25 – Jun 25 |
| Snap beans | Sow outdoors | May 11 – Jul 27 |
| Sweet corn | Sow outdoors | May 11 – Jun 24 |
| Watermelon & cantaloupe | Sow outdoors | May 25 – Jun 25 |
| Okra | Sow outdoors | May 18 – Jun 10 |
| Peas | Sow outdoors (spring) | Mar 25 – May 10 |
| Potatoes | Plant outdoors (spring) | Mar 25 – May 25 |
| Onions | Start seeds indoors (spring) | Feb 11 – Mar 10 |
| Onions | Transplant outdoors (spring) | Apr 11 – May 10 |
| Broccoli | Start seeds indoors (spring) | Mar 7 – Apr 10 |
| Broccoli | Transplant outdoors (spring) | Apr 11 – May 10 |
| Broccoli | Start seeds indoors (fall) | Jun 14 – Jun 24 |
| Broccoli | Transplant outdoors (fall) | Jul 14 – Jul 25 |
| Cabbage | Start seeds indoors (spring) | Feb 25 – Mar 25 |
| Cabbage | Transplant outdoors (spring) | Mar 25 – Apr 25 |
| Cabbage | Start seeds indoors (fall) | Jun 4 – Jul 4 |
| Cabbage | Transplant outdoors (fall) | Jul 4 – Aug 4 |
| Leaf lettuce | Sow outdoors (spring) | Mar 25 – Jun 10 |
| Leaf lettuce | Sow outdoors (fall) | Jul 4 – Aug 20 |
| Spinach | Sow outdoors (spring) | Mar 18 – May 1 |
| Spinach | Sow outdoors (fall) | Jul 21 – Aug 25 |
| Radishes | Sow outdoors (spring) | Mar 25 – May 15 |
| Radishes | Sow outdoors (fall) | Jul 4 – Sep 4 |
| Kale | Sow outdoors (spring) | Apr 11 – May 1 |
| Kale | Sow outdoors (fall) | Jun 27 – Aug 4 |
| Carrots | Sow outdoors (spring) | Apr 25 – Jun 10 |
| Carrots | Sow outdoors (fall) | Jun 4 – Jul 20 |
| Garlic | Plant outdoors (fall) | Oct 4 – Nov 4 |
Where these dates come from
ZIP code 52309 is matched to the NOAA station Maquoketa, IA, 17.7 km away, at 668 ft elevation (87 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Maquoketa, IA (used) | 668 ft | Apr 25 | Oct 14 |
| Lowden, IA | 738 ft | Apr 27 | Oct 10 |
| Cascade, IA | 814 ft | Apr 28 | Oct 10 |
| Anamosa 1 Wnw, IA | 805 ft | May 1 | Oct 4 |
Frost dates near Monmouth
- Baldwin, IA 52207 · last Apr 25, first Oct 14
- Wyoming, IA 52362 · last May 1, first Oct 4
- Onslow, IA 52321 · last Apr 28, first Oct 10
- Oxford Junction, IA 52323 · last Apr 27, first Oct 10
- Lost Nation, IA 52254 · last Apr 25, first Oct 14
- Maquoketa, IA 52060 · last Apr 25, first Oct 14
- Center Junction, IA 52212 · last May 1, first Oct 4
- Olin, IA 52320 · last May 1, first Oct 4
Frequently asked questions
- When is the last frost in Monmouth, IA?
- For ZIP code 52309, the average last spring frost (32°F) is April 25, based on NOAA 1991-2020 climate normals for the Maquoketa, IA weather station. There is a 1-in-10 chance of a frost after May 9.
- When is the first frost in Monmouth, IA?
- The average first fall frost (32°F) is October 14. 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 52309?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 171 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.