Joliet, IL planting zone & frost dates
Joliet is in USDA hardiness zone 6a. The last spring frost usually comes around April 19 and the first fall frost around October 25, for a growing season of about 188 days.
Planting calendar for Joliet
Dates are counted from the average last spring frost (April 19) using the typical timing recommended by U.S. extension services. Warm-season crops go out only after the danger of frost has passed and the soil has warmed.
| Crop | When |
|---|---|
| Tomatoes | Start seeds indoors: Feb 22 – Mar 8 Transplant outdoors: Apr 26 – May 3 |
| Peppers | Start seeds indoors: Feb 8 – Feb 22 Transplant outdoors: May 3 – May 10 |
| Eggplant | Start seeds indoors: Feb 8 – Feb 22 Transplant outdoors: May 3 – May 10 |
| Broccoli | Start seeds indoors: Feb 8 – Feb 22 Transplant outdoors: Mar 22 – Apr 5 |
| Cabbage | Start seeds indoors: Feb 8 – Feb 22 Transplant outdoors: Mar 22 – Apr 5 |
| Onions (sets) | Plant outdoors: Mar 22 – Apr 5 |
| Peas | Sow outdoors: Mar 8 – Mar 22 |
| Spinach | Sow outdoors: Mar 8 – Mar 22 |
| Lettuce | Sow outdoors: Mar 22 – Apr 5 |
| Carrots | Sow outdoors: Mar 22 – Apr 5 |
| Potatoes | Plant outdoors: Mar 22 – Apr 5 |
| Beans | Sow outdoors: Apr 26 – May 3 |
| Sweet corn | Sow outdoors: Apr 26 – May 3 |
| Cucumbers | Sow outdoors: Apr 26 – May 3 |
| Squash & zucchini | Sow outdoors: Apr 26 – May 3 |
| Basil | Start seeds indoors: Mar 8 – Mar 22 Transplant outdoors: Apr 26 – May 3 |
Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Aug 30 (8 weeks before the average first fall frost on Oct 25).
Useful for zone 6a gardens
- Seed starting kit with dome — to start seeds indoors before the last frost
- LED grow light for seedlings — stops leggy seedlings
- Frost cloth / plant covers — for late spring and early fall frosts
- Soil thermometer — warm-season crops need soil above 60°F
- Cold frame / mini greenhouse — adds weeks to a short season
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Frost risk in detail
| 90% chance | 50% chance | 10% chance | |
|---|---|---|---|
| Last 32°F frost in spring is after | Apr 3 | Apr 19 | May 7 |
| First 32°F frost in fall is before | Nov 6 | Oct 25 | Oct 12 |
How to read it: in spring there is a 10% chance of a frost after May 7, so that is a safe date for tender plants. In fall there is a 10% chance of frost before October 12. A hard freeze (28°F) usually ends around April 5.
Hardiness zone by ZIP code in Joliet
- 60431 zone 5b
- 60432 zone 6a
- 60433 zone 6a
- 60434 zone 6a
- 60435 zone 6a
- 60436 zone 6a
Nearby cities
- Crest Hill zone 6a, last frost Apr 20
- Lockport zone 6a, last frost Apr 20
- Shorewood zone 5b, last frost Apr 19
- New Lenox zone 6a, last frost Apr 19
- Romeoville zone 6a, last frost Apr 20
- Plainfield zone 5b, last frost Apr 20
- Homer Glen zone 6a, last frost Apr 20
- Lemont zone 6a, last frost Apr 20
Questions
What growing zone is Joliet, IL?
Joliet is in USDA Plant Hardiness Zone 6a (average extreme winter low -10°F to -5°F), according to the USDA 2023 map. Some ZIP codes of the city fall in zone 5b.
When is the last frost in Joliet?
The average last spring frost (32°F) in Joliet is April 19. There is still a 10% chance of frost until May 7.
When can I plant tomatoes in Joliet?
Transplant tomatoes outdoors 1–2 weeks after the average last frost: around Apr 26 – May 3. Start seeds indoors 6–8 weeks before the last frost.
Frost dates: NOAA U.S. Climate Normals 1991–2020, station Joliet Brandon Rd Dam, IL (USC00114530), 2.9 km (1.8 mi) from the city center, elevation 166 m, based on 30 years of records. Hardiness zone: USDA Plant Hardiness Zone Map 2023 for the ZIP code nearest to the city center. Microclimates (valleys, hills, cities, coasts) can be warmer or colder: check the local forecast before planting. How we calculate the data.