Saint Charles, MO planting zone & frost dates
Saint Charles is in USDA hardiness zone 7a. The last spring frost usually comes around April 8 and the first fall frost around October 29, for a growing season of about 203 days.
Planting calendar for Saint Charles
Dates are counted from the average last spring frost (April 8) 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 11 – Feb 25 Transplant outdoors: Apr 15 – Apr 22 |
| Peppers | Start seeds indoors: Jan 28 – Feb 11 Transplant outdoors: Apr 22 – Apr 29 |
| Eggplant | Start seeds indoors: Jan 28 – Feb 11 Transplant outdoors: Apr 22 – Apr 29 |
| Broccoli | Start seeds indoors: Jan 28 – Feb 11 Transplant outdoors: Mar 11 – Mar 25 |
| Cabbage | Start seeds indoors: Jan 28 – Feb 11 Transplant outdoors: Mar 11 – Mar 25 |
| Onions (sets) | Plant outdoors: Mar 11 – Mar 25 |
| Peas | Sow outdoors: Feb 25 – Mar 11 |
| Spinach | Sow outdoors: Feb 25 – Mar 11 |
| Lettuce | Sow outdoors: Mar 11 – Mar 25 |
| Carrots | Sow outdoors: Mar 11 – Mar 25 |
| Potatoes | Plant outdoors: Mar 11 – Mar 25 |
| Beans | Sow outdoors: Apr 15 – Apr 22 |
| Sweet corn | Sow outdoors: Apr 15 – Apr 22 |
| Cucumbers | Sow outdoors: Apr 15 – Apr 22 |
| Squash & zucchini | Sow outdoors: Apr 15 – Apr 22 |
| Basil | Start seeds indoors: Feb 25 – Mar 11 Transplant outdoors: Apr 15 – Apr 22 |
Fall garden: cool-season crops like lettuce, spinach and kale can be sown again around Sep 3 (8 weeks before the average first fall frost on Oct 29).
Useful for zone 7a 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
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Frost risk in detail
| 90% chance | 50% chance | 10% chance | |
|---|---|---|---|
| Last 32°F frost in spring is after | Mar 23 | Apr 8 | Apr 24 |
| First 32°F frost in fall is before | Nov 12 | Oct 29 | Oct 16 |
How to read it: in spring there is a 10% chance of a frost after April 24, so that is a safe date for tender plants. In fall there is a 10% chance of frost before October 16. A hard freeze (28°F) usually ends around March 30.
Hardiness zone by ZIP code in Saint Charles
- 63301 zone 6b
- 63302 zone 7a
- 63303 zone 7a
- 63304 zone 6b
Nearby cities
- Bridgeton zone 6b, last frost Apr 2
- Maryland Heights zone 7a, last frost Apr 2
- Hazelwood zone 7a, last frost Apr 2
- Saint Ann zone 7a, last frost Apr 2
- Creve Coeur zone 7a, last frost Apr 4
- Overland zone 7a, last frost Apr 2
- Saint Peters zone 6b, last frost Apr 9
- Chesterfield zone 7a, last frost Apr 4
Questions
What growing zone is Saint Charles, MO?
Saint Charles is in USDA Plant Hardiness Zone 7a (average extreme winter low 0°F to 5°F), according to the USDA 2023 map. Some ZIP codes of the city fall in zone 6b.
When is the last frost in Saint Charles?
The average last spring frost (32°F) in Saint Charles is April 8. There is still a 10% chance of frost until April 24.
When can I plant tomatoes in Saint Charles?
Transplant tomatoes outdoors 1–2 weeks after the average last frost: around Apr 15 – Apr 22. Start seeds indoors 6–8 weeks before the last frost.
Frost dates: NOAA U.S. Climate Normals 1991–2020, station St Charles Elm Pt, MO (USC00237397), 4.4 km (2.7 mi) from the city center, elevation 144 m, based on 27 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.