Frost dates for 62435Janesville, IL
The average last spring frost in Janesville is April 15 and the average first fall frost is October 24, giving a typical growing season of about 189 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 15
- Average first fall frost
- Oct 24
- Growing season
- 189 days
Safer after Apr 30 (1-in-10 risk)
Possible by Oct 9 (1-in-10 risk)
Last frost typically in 167 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 12 · Apr 26 · May 13 | Sep 27 · Oct 13 · Oct 25 | 168 days | 100% |
| Frost / freeze (32°F) | Apr 2 · Apr 15 · Apr 30 | Oct 9 · Oct 24 · Nov 5 | 189 days | 100% |
| Hard freeze (28°F) | Mar 19 · Apr 2 · Apr 18 | Oct 21 · Nov 3 · Nov 18 | 214 days | 100% |
Planting calendar for Janesville
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 15 – May 21 |
| Tomatoes | Transplant outdoors | May 1 – Jul 4 |
| Peppers | Start seeds indoors | Mar 15 – Apr 15 |
| Peppers | Transplant outdoors | May 15 – Jun 15 |
| Eggplant | Start seeds indoors | Apr 1 – Apr 30 |
| Eggplant | Transplant outdoors | May 15 – Jun 15 |
| Cucumbers | Sow outdoors | May 15 – Jul 14 |
| Summer squash | Sow outdoors | May 1 – Jun 15 |
| Winter squash & pumpkins | Sow outdoors | May 15 – Jun 15 |
| Snap beans | Sow outdoors | May 1 – Aug 6 |
| Sweet corn | Sow outdoors | May 1 – Jul 4 |
| Watermelon & cantaloupe | Sow outdoors | May 15 – Jun 15 |
| Okra | Sow outdoors | May 8 – May 31 |
| Peas | Sow outdoors (spring) | Mar 15 – Apr 30 |
| Potatoes | Plant outdoors (spring) | Mar 15 – May 15 |
| Onions | Start seeds indoors (spring) | Feb 1 – Feb 28 |
| Onions | Transplant outdoors (spring) | Apr 1 – Apr 30 |
| Broccoli | Start seeds indoors (spring) | Feb 25 – Mar 31 |
| Broccoli | Transplant outdoors (spring) | Apr 1 – Apr 30 |
| Broccoli | Start seeds indoors (fall) | Jun 24 – Jul 4 |
| Broccoli | Transplant outdoors (fall) | Jul 24 – Aug 4 |
| Cabbage | Start seeds indoors (spring) | Feb 15 – Mar 15 |
| Cabbage | Transplant outdoors (spring) | Mar 15 – Apr 15 |
| Cabbage | Start seeds indoors (fall) | Jun 14 – Jul 14 |
| Cabbage | Transplant outdoors (fall) | Jul 14 – Aug 14 |
| Leaf lettuce | Sow outdoors (spring) | Mar 15 – May 31 |
| Leaf lettuce | Sow outdoors (fall) | Jul 14 – Aug 30 |
| Spinach | Sow outdoors (spring) | Mar 8 – Apr 21 |
| Spinach | Sow outdoors (fall) | Jul 31 – Sep 4 |
| Radishes | Sow outdoors (spring) | Mar 15 – May 5 |
| Radishes | Sow outdoors (fall) | Jul 14 – Sep 14 |
| Kale | Sow outdoors (spring) | Apr 1 – Apr 21 |
| Kale | Sow outdoors (fall) | Jul 7 – Aug 14 |
| Carrots | Sow outdoors (spring) | Apr 15 – May 31 |
| Carrots | Sow outdoors (fall) | Jun 14 – Jul 30 |
| Garlic | Plant outdoors (fall) | Oct 14 – Nov 14 |
Where these dates come from
ZIP code 62435 is matched to the NOAA station Mattoon Coles Co Ap, IL, 11.9 km away, at 721 ft elevation (32 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Mattoon Coles Co Ap, IL (used) | 721 ft | Apr 15 | Oct 24 |
| Charleston, IL | 700 ft | Apr 15 | Oct 23 |
| Mattoon, IL | 701 ft | Apr 11 | Oct 29 |
| Neoga 4Nw, IL | 643 ft | Apr 16 | Oct 20 |
Frost dates near Janesville
- Lerna, IL 62440 · last Apr 15, first Oct 24
- Trilla, IL 62469 · last Apr 15, first Oct 24
- Toledo, IL 62468 · last Apr 15, first Oct 23
- Charleston, IL 61920 · last Apr 15, first Oct 23
- Greenup, IL 62428 · last Apr 15, first Oct 23
- Mattoon, IL 61938 · last Apr 15, first Oct 24
- Jewett, IL 62436 · last Apr 13, first Oct 22
- Neoga, IL 62447 · last Apr 16, first Oct 22
Frequently asked questions
- When is the last frost in Janesville, IL?
- For ZIP code 62435, the average last spring frost (32°F) is April 15, based on NOAA 1991-2020 climate normals for the Mattoon Coles Co Ap, IL weather station. There is a 1-in-10 chance of a frost after April 30.
- When is the first frost in Janesville, IL?
- The average first fall frost (32°F) is October 24. There is a 1-in-10 chance of frost by October 9, so tender plants are at risk from that point on.
- How long is the growing season in 62435?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 189 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.