Frost dates for 60435Joliet, IL
The average last spring frost in Joliet is April 20 and the average first fall frost is October 22, giving a typical growing season of about 184 days. Dates are based on NOAA 1991-2020 climate normals.
- Average last spring frost
- Apr 20
- Average first fall frost
- Oct 22
- Growing season
- 184 days
Safer after May 6 (1-in-10 risk)
Possible by Oct 7 (1-in-10 risk)
Last frost typically in 168 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 17 · May 1 · May 17 | Sep 28 · Oct 12 · Oct 24 | 162 days | 100% |
| Frost / freeze (32°F) | Apr 7 · Apr 20 · May 6 | Oct 7 · Oct 22 · Nov 3 | 184 days | 100% |
| Hard freeze (28°F) | Mar 27 · Apr 8 · Apr 23 | Oct 19 · Nov 1 · Nov 15 | 206 days | 100% |
Planting calendar for Joliet
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 20 – May 26 |
| Tomatoes | Transplant outdoors | May 6 – Jul 2 |
| Peppers | Start seeds indoors | Mar 20 – Apr 20 |
| Peppers | Transplant outdoors | May 20 – Jun 20 |
| Eggplant | Start seeds indoors | Apr 6 – May 5 |
| Eggplant | Transplant outdoors | May 20 – Jun 20 |
| Cucumbers | Sow outdoors | May 20 – Jul 12 |
| Summer squash | Sow outdoors | May 6 – Jun 20 |
| Winter squash & pumpkins | Sow outdoors | May 20 – Jun 20 |
| Snap beans | Sow outdoors | May 6 – Aug 4 |
| Sweet corn | Sow outdoors | May 6 – Jul 2 |
| Watermelon & cantaloupe | Sow outdoors | May 20 – Jun 20 |
| Okra | Sow outdoors | May 13 – Jun 5 |
| Peas | Sow outdoors (spring) | Mar 20 – May 5 |
| Potatoes | Plant outdoors (spring) | Mar 20 – May 20 |
| Onions | Start seeds indoors (spring) | Feb 6 – Mar 5 |
| Onions | Transplant outdoors (spring) | Apr 6 – May 5 |
| Broccoli | Start seeds indoors (spring) | Mar 2 – Apr 5 |
| Broccoli | Transplant outdoors (spring) | Apr 6 – May 5 |
| Broccoli | Start seeds indoors (fall) | Jun 22 – Jul 2 |
| Broccoli | Transplant outdoors (fall) | Jul 22 – Aug 2 |
| Cabbage | Start seeds indoors (spring) | Feb 20 – Mar 20 |
| Cabbage | Transplant outdoors (spring) | Mar 20 – Apr 20 |
| Cabbage | Start seeds indoors (fall) | Jun 12 – Jul 12 |
| Cabbage | Transplant outdoors (fall) | Jul 12 – Aug 12 |
| Leaf lettuce | Sow outdoors (spring) | Mar 20 – Jun 5 |
| Leaf lettuce | Sow outdoors (fall) | Jul 12 – Aug 28 |
| Spinach | Sow outdoors (spring) | Mar 13 – Apr 26 |
| Spinach | Sow outdoors (fall) | Jul 29 – Sep 2 |
| Radishes | Sow outdoors (spring) | Mar 20 – May 10 |
| Radishes | Sow outdoors (fall) | Jul 12 – Sep 12 |
| Kale | Sow outdoors (spring) | Apr 6 – Apr 26 |
| Kale | Sow outdoors (fall) | Jul 5 – Aug 12 |
| Carrots | Sow outdoors (spring) | Apr 20 – Jun 5 |
| Carrots | Sow outdoors (fall) | Jun 12 – Jul 28 |
| Garlic | Plant outdoors (fall) | Oct 12 – Nov 12 |
Where these dates come from
ZIP code 60435 is matched to the NOAA station Romeoville Wfo, IL, 7.5 km away, at 660 ft elevation (14 ft higher than the ZIP code's center). Nearby stations for comparison:
| Station | Elevation | Avg last frost | Avg first frost |
|---|---|---|---|
| Romeoville Wfo, IL (used) | 660 ft | Apr 20 | Oct 22 |
| Joliet Brandon Rd Dam, IL | 543 ft | Apr 19 | Oct 25 |
| Channahon Dresden Isl Dam, IL | 505 ft | Apr 16 | Oct 26 |
| Little Red School Hse, IL | 715 ft | Apr 19 | Oct 22 |
Frost dates near Joliet
- Crest Hill, IL 60403 · last Apr 20, first Oct 22
- Joliet, IL 60434 · last Apr 19, first Oct 25
- Plainfield, IL 60586 · last Apr 20, first Oct 22
- Shorewood, IL 60404 · last Apr 19, first Oct 25
- Lockport, IL 60441 · last Apr 20, first Oct 22
- Romeoville, IL 60446 · last Apr 20, first Oct 22
- Elwood, IL 60421 · last Apr 19, first Oct 25
- Channahon, IL 60410 · last Apr 16, first Oct 26
Frequently asked questions
- When is the last frost in Joliet, IL?
- For ZIP code 60435, the average last spring frost (32°F) is April 20, based on NOAA 1991-2020 climate normals for the Romeoville Wfo, IL weather station. There is a 1-in-10 chance of a frost after May 6.
- When is the first frost in Joliet, IL?
- The average first fall frost (32°F) is October 22. There is a 1-in-10 chance of frost by October 7, so tender plants are at risk from that point on.
- How long is the growing season in 60435?
- In half of years, the frost-free season (between the last and first 32°F frost) is at least 184 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.