St. Louis, Missouri: planting zone & frost dates
St. Louis is in USDA plant hardiness zone 7a, where the average coldest winter night reaches 0 to 5°F (-17.8 to -15.0°C). The typical last spring frost is around Apr 7 and the first fall frost around Oct 31.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | Apr 18 | Oct 24 |
| Typical planning date (30% risk) | Apr 7 | Oct 31 |
| Median (50%) | Apr 1 | Nov 4 |
How to read this: after the spring "10% risk" date, a 32°F frost happens in only about 1 year in 10. In fall, the "10% risk" date is the early end — a frost before it happens about 1 year in 10.
Frost data comes from NOAA station ST LOUIS SCI CTR, MO (USC00237452), 1.4 mi (2.3 km) from the city center and 49 ft higher than the city center (+15 m). Record used for the 1991–2020 normals: 25 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across St. Louis
All 20 ZIP codes covering St. Louis are in zone 7a.
Vegetable planting calendar for St. Louis
Dates are counted from the 30%-risk frost dates above (last frost Apr 7, first frost Oct 31). Shift a week later in cold spots or low-lying ground.
| Crop | Start indoors | Transplant / plant out | Direct sow | Fall crop sow/plant |
|---|---|---|---|---|
| Tomato | Feb 10 – Feb 24 | Apr 14 – Apr 28 | — | — |
| Pepper | Jan 27 – Feb 10 | Apr 21 – May 5 | — | — |
| Lettuce | Feb 24 – Mar 10 | Mar 24 – Apr 14 | Mar 10 – Apr 21 | Aug 22 – Sep 19 |
| Green Beans | — | — | Apr 14 – May 19 | Aug 8 – Aug 22 |
| Sweet Corn | — | — | Apr 14 – May 12 | — |
| Zucchini & Summer Squash | Mar 10 – Mar 17 | Apr 14 – Apr 28 | Apr 14 – May 5 | Aug 8 – Aug 22 |
| Cucumber | Mar 10 – Mar 17 | Apr 21 – Apr 28 | Apr 14 – May 5 | Aug 8 – Aug 22 |
| Carrot | — | — | Mar 17 – Apr 21 | Aug 8 – Aug 22 |
| Onion | Jan 13 – Jan 27 | Mar 10 – Mar 24 | — | — |
| Potato | — | Mar 10 – Mar 31 | — | — |
| Basil | Feb 24 – Mar 10 | Apr 21 – May 5 | Apr 21 – May 12 | — |
| Spinach | — | — | Feb 24 – Mar 24 | Sep 5 – Oct 3 |
| Kale | Feb 10 – Feb 24 | Mar 10 – Mar 31 | Mar 10 – Mar 31 | Aug 22 – Sep 19 |
| Broccoli | Feb 10 – Feb 24 | Mar 24 – Apr 14 | — | Aug 8 – Aug 22 |
| Peas | — | — | Feb 24 – Mar 17 | Aug 22 – Sep 5 |
| Eggplant | Jan 27 – Feb 10 | Apr 21 – May 5 | — | — |
| Cabbage | Feb 10 – Feb 24 | Mar 10 – Mar 24 | — | Aug 8 – Aug 22 |
| Radish | — | — | Mar 3 – Apr 21 | Sep 19 – Oct 17 |
| Strawberry | — | Mar 10 – Mar 31 | — | — |
| Beets | — | — | Mar 17 – Apr 28 | Aug 22 – Sep 5 |
Nearby cities in Missouri
- O'Fallon — zone 6b, last frost Apr 16, first frost Oct 20
- Columbia — zone 6b, last frost Apr 12, first frost Oct 25
- Springfield — zone 6b, last frost Apr 16, first frost Oct 22
- Independence — zone 6b, last frost Apr 16, first frost Oct 22
- Lee's Summit — zone 6b, last frost Apr 13, first frost Oct 23
- Kansas City — zone 6b, last frost Apr 10, first frost Oct 29
More: all Missouri cities · other zone 7a cities: Louisville, KY, Wichita, KS, Cleveland, OH, Lexington, KY, Boise, ID, Amarillo, TX, Providence, RI, Paterson, NJ
St. Louis gardening questions
When is the last frost in St. Louis, MO?
Plan around Apr 7. At NOAA's St Louis Science Center, MO station, 1.4 mi from the city center, there is a 30% chance of a 32°F frost after that date. Half of springs have their last frost by Apr 1, and after Apr 18 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Mar 22. The 90% and 10% dates are 35 days apart, close to the 36-day median for cities on this site.
When should I plant tomatoes in St. Louis, MO?
Start seeds indoors Feb 10 – Feb 24 and set transplants outside Apr 14 – Apr 28, once nights stay above 50°F and the soil is near 60°F. That leaves 207 days between the 30% frost dates, enough for most varieties including 80–85-day slicers. More: tomato planting dates by zone.
How long is the growing season in St. Louis?
About 218 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 198 days, and in 1 year in 10 it runs 240 days or more. In fall there is a 10% chance of frost by Oct 24 and a 30% chance by Oct 31. That is the longest of the 7 Missouri cities on this site.
When should I plant a fall garden in St. Louis?
Count back from the first fall frost (Oct 31): transplant broccoli Aug 8 – Aug 22; sow kale Aug 22 – Sep 19; sow lettuce Aug 22 – Sep 19; sow radishes Sep 19 – Oct 17. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Nov 15. How the math works: succession and fall planting.
Did St. Louis's hardiness zone change on the 2023 map?
Yes. Most of St. Louis was zone 6b on the 2012 map and is zone 7a on the 2023 map — half a zone warmer, like about 56% of U.S. ZIP codes. The shift comes from a newer 1991–2020 averaging period plus more weather stations and better mapping; it does not mean last frost comes earlier. Why the 2023 map is warmer.
How does St. Louis compare with O'Fallon, MO?
St. Louis is zone 7a and O'Fallon is zone 6b. The typical last spring frost in St. Louis (Apr 7) comes about 9 days earlier than in O'Fallon, MO (Apr 16), 28 miles away, and the first fall frost is Oct 31 versus Oct 20. St. Louis sits about 155 ft lower, which explains part of the gap. The two cities use different NOAA stations.