Olathe, Kansas: planting zone & frost dates
Olathe is in USDA plant hardiness zone 6b, where the average coldest winter night reaches -5 to 0°F (-20.6 to -17.8°C). The typical last spring frost is around Apr 16 and the first fall frost around Oct 23.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | Apr 24 | Oct 13 |
| Typical planning date (30% risk) | Apr 16 | Oct 23 |
| Median (50%) | Apr 10 | Oct 29 |
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 OLATHE 3E, KS (USC00145972), 3.2 mi (5.2 km) from the city center and 16 ft higher than the city center (+5 m). Record used for the 1991–2020 normals: 17 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Olathe
All 2 ZIP codes covering Olathe are in zone 6b.
Vegetable planting calendar for Olathe
Dates are counted from the 30%-risk frost dates above (last frost Apr 16, first frost Oct 23). 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 19 – Mar 5 | Apr 23 – May 7 | — | — |
| Pepper | Feb 5 – Feb 19 | Apr 30 – May 14 | — | — |
| Lettuce | Mar 5 – Mar 19 | Apr 2 – Apr 23 | Mar 19 – Apr 30 | Aug 14 – Sep 11 |
| Green Beans | — | — | Apr 23 – May 28 | Jul 31 – Aug 14 |
| Sweet Corn | — | — | Apr 23 – May 21 | — |
| Zucchini & Summer Squash | Mar 19 – Mar 26 | Apr 23 – May 7 | Apr 23 – May 14 | Jul 31 – Aug 14 |
| Cucumber | Mar 19 – Mar 26 | Apr 30 – May 7 | Apr 23 – May 14 | Jul 31 – Aug 14 |
| Carrot | — | — | Mar 26 – Apr 30 | Jul 31 – Aug 14 |
| Onion | Jan 22 – Feb 5 | Mar 19 – Apr 2 | — | — |
| Potato | — | Mar 19 – Apr 9 | — | — |
| Basil | Mar 5 – Mar 19 | Apr 30 – May 14 | Apr 30 – May 21 | — |
| Spinach | — | — | Mar 5 – Apr 2 | Aug 28 – Sep 25 |
| Kale | Feb 19 – Mar 5 | Mar 19 – Apr 9 | Mar 19 – Apr 9 | Aug 14 – Sep 11 |
| Broccoli | Feb 19 – Mar 5 | Apr 2 – Apr 23 | — | Jul 31 – Aug 14 |
| Peas | — | — | Mar 5 – Mar 26 | Aug 14 – Aug 28 |
| Eggplant | Feb 5 – Feb 19 | Apr 30 – May 14 | — | — |
| Cabbage | Feb 19 – Mar 5 | Mar 19 – Apr 2 | — | Jul 31 – Aug 14 |
| Radish | — | — | Mar 12 – Apr 30 | Sep 11 – Oct 9 |
| Strawberry | — | Mar 19 – Apr 9 | — | — |
| Beets | — | — | Mar 26 – May 7 | Aug 14 – Aug 28 |
Nearby cities in Kansas
- Overland Park — zone 6b, last frost Apr 16, first frost Oct 23
- Kansas City — zone 6b, last frost Apr 10, first frost Oct 29
- Lawrence — zone 6b, last frost Apr 17, first frost Oct 22
- Topeka — zone 6b, last frost Apr 20, first frost Oct 17
- Wichita — zone 7a, last frost Apr 16, first frost Oct 21
More: all Kansas cities · other zone 6b cities: Columbus, OH, Indianapolis, IN, Boston, MA, Detroit, MI, Kansas City, MO, Cincinnati, OH, Pittsburgh, PA, Buffalo, NY
Olathe gardening questions
When is the last frost in Olathe, KS?
Plan around Apr 16. At NOAA's Olathe 3E, KS station, 3.2 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 10, and after Apr 24 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Mar 31. The last frost is fairly predictable here: only 28 days separate the 90% and 10% dates (median for cities on this site: 36 days).
When should I plant tomatoes in Olathe, KS?
Start seeds indoors Feb 19 – Mar 5 and set transplants outside Apr 23 – May 7, once nights stay above 50°F and the soil is near 60°F. That leaves 190 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 Olathe?
About 202 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 181 days, and in 1 year in 10 it runs 223 days or more. In fall there is a 10% chance of frost by Oct 13 and a 30% chance by Oct 23. That ranks 3rd longest of 6 Kansas cities on this site.
When should I plant a fall garden in Olathe?
Count back from the first fall frost (Oct 23): transplant broccoli Jul 31 – Aug 14; sow kale Aug 14 – Sep 11; sow lettuce Aug 14 – Sep 11; sow radishes Sep 11 – Oct 9. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Nov 6. How the math works: succession and fall planting.
Did Olathe's hardiness zone change on the 2023 map?
Yes. Most of Olathe was zone 6a on the 2012 map and is zone 6b 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 Olathe compare with Kansas City, KS?
Both are in zone 6b. The typical last spring frost in Olathe (Apr 16) comes about 6 days later than in Kansas City, KS (Apr 10), 17 miles away, and the first fall frost is Oct 23 versus Oct 29. The two cities use different NOAA stations.