Frost dates for 52310Monticello, IA
The average last spring frost in Monticello is May 1 and the average first fall frost is October 4, giving a typical growing season of about 154 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- May 1
- Average first fall frost
- Oct 4
- Growing season
- 154 days
Safer after May 18 (1-in-10 risk)
Possible by Sep 21 (1-in-10 risk)
Last frost typically in 180 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 28 · May 13 · May 28 | Sep 14 · Sep 27 · Oct 8 | 137 days | 100% |
| Frost / freeze (32°F) | Apr 18 · May 1 · May 18 | Sep 21 · Oct 4 · Oct 18 | 154 days | 100% |
| Hard freeze (28°F) | Apr 6 · Apr 21 · May 6 | Oct 1 · Oct 16 · Oct 30 | 175 days | 100% |
Planting calendar for Monticello
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 31 – Jun 6 |
| Tomatoes | Transplant outdoors | May 17 – Jun 14 |
| Peppers | Start seeds indoors | Mar 31 – May 1 |
| Peppers | Transplant outdoors | May 31 – Jul 1 |
| Eggplant | Start seeds indoors | Apr 17 – May 16 |
| Eggplant | Transplant outdoors | May 31 – Jul 1 |
| Cucumbers | Sow outdoors | May 31 – Jun 24 |
| Summer squash | Sow outdoors | May 17 – Jul 1 |
| Winter squash & pumpkins | Sow outdoors | May 31 – Jul 1 |
| Snap beans | Sow outdoors | May 17 – Jul 17 |
| Sweet corn | Sow outdoors | May 17 – Jun 14 |
| Watermelon & cantaloupe | Sow outdoors | May 31 – Jul 1 |
| Okra | Sow outdoors | May 24 – Jun 16 |
| Peas | Sow outdoors (spring) | Mar 31 – May 16 |
| Potatoes | Plant outdoors (spring) | Mar 31 – May 31 |
| Onions | Start seeds indoors (spring) | Feb 17 – Mar 16 |
| Onions | Transplant outdoors (spring) | Apr 17 – May 16 |
| Broccoli | Start seeds indoors (spring) | Mar 13 – Apr 16 |
| Broccoli | Transplant outdoors (spring) | Apr 17 – May 16 |
| Broccoli | Start seeds indoors (fall) | Jun 4 – Jun 14 |
| Broccoli | Transplant outdoors (fall) | Jul 4 – Jul 15 |
| Cabbage | Start seeds indoors (spring) | Mar 3 – Mar 31 |
| Cabbage | Transplant outdoors (spring) | Mar 31 – May 1 |
| Cabbage | Start seeds indoors (fall) | May 25 – Jun 24 |
| Cabbage | Transplant outdoors (fall) | Jun 24 – Jul 25 |
| Leaf lettuce | Sow outdoors (spring) | Mar 31 – Jun 16 |
| Leaf lettuce | Sow outdoors (fall) | Jun 24 – Aug 10 |
| Spinach | Sow outdoors (spring) | Mar 24 – May 7 |
| Spinach | Sow outdoors (fall) | Jul 11 – Aug 15 |
| Radishes | Sow outdoors (spring) | Mar 31 – May 21 |
| Radishes | Sow outdoors (fall) | Jun 24 – Aug 25 |
| Kale | Sow outdoors (spring) | Apr 17 – May 7 |
| Kale | Sow outdoors (fall) | Jun 17 – Jul 25 |
| Carrots | Sow outdoors (spring) | May 1 – Jun 16 |
| Carrots | Sow outdoors (fall) | May 25 – Jul 10 |
| Garlic | Plant outdoors (fall) | Sep 24 – Oct 25 |
Where these dates come from
ZIP code 52310 is matched to the NOAA station Anamosa 1 Wnw, IA, 15.5 km away, at 805 ft elevation (64 ft lower than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Anamosa 1 Wnw, IA (used) | 805 ft | May 1 | Oct 4 |
| Cascade, IA | 814 ft | Apr 28 | Oct 10 |
| Anamosa 3 Ssw, IA | 906 ft | Apr 27 | Oct 13 |
| Coggon, IA | 903 ft | May 3 | Oct 7 |
Frost dates near Monticello
- Langworthy, IA 52252 · last May 1, first Oct 4
- Hopkinton, IA 52237 · last Apr 28, first Oct 10
- Anamosa, IA 52205 · last May 1, first Oct 4
- Center Junction, IA 52212 · last May 1, first Oct 4
- Cascade, IA 52033 · last Apr 28, first Oct 10
- Prairieburg, IA 52219 · last May 3, first Oct 7
- Worthington, IA 52078 · last Apr 28, first Oct 10
- Onslow, IA 52321 · last Apr 28, first Oct 10
Frequently asked questions
- When is the last frost in Monticello, IA?
- For ZIP code 52310, the average last spring frost (32°F) is May 1, based on NOAA 1991-2020 climate normals for the Anamosa 1 Wnw, IA weather station. There is a 1-in-10 chance of a frost after May 18.
- When is the first frost in Monticello, IA?
- The average first fall frost (32°F) is October 4. 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 52310?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 154 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.