Lakewood, Colorado: planting zone & frost dates
Lakewood is in USDA plant hardiness zone 6a, where the average coldest winter night reaches -10 to -5°F (-23.3 to -20.6°C). The typical last spring frost is around May 8 and the first fall frost around Oct 2.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | May 18 | Sep 24 |
| Typical planning date (30% risk) | May 8 | Oct 2 |
| Median (50%) | May 3 | Oct 7 |
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 LAKEWOOD, CO (USC00054762), 3.5 mi (5.6 km) from the city center and 16 ft lower than the city center (-5 m). Record used for the 1991–2020 normals: 24 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Lakewood
Lakewood spans more than one half-zone. Share of the city's land area by zone (via its 10 ZIP codes): 6a (92%), 5b (8%). The headline zone is the one covering the most land. Look up your ZIP for your exact zone.
Vegetable planting calendar for Lakewood
Dates are counted from the 30%-risk frost dates above (last frost May 8, first frost Oct 2). Shift a week later in cold spots or low-lying ground.
| Crop | Start indoors | Transplant / plant out | Direct sow | Fall crop sow/plant |
|---|---|---|---|---|
| Tomato | Mar 13 – Mar 27 | May 15 – May 29 | — | — |
| Pepper | Feb 27 – Mar 13 | May 22 – Jun 5 | — | — |
| Lettuce | Mar 27 – Apr 10 | Apr 24 – May 15 | Apr 10 – May 22 | Jul 24 – Aug 21 |
| Green Beans | — | — | May 15 – Jun 19 | Jul 10 – Jul 24 |
| Sweet Corn | — | — | May 15 – Jun 12 | — |
| Zucchini & Summer Squash | Apr 10 – Apr 17 | May 15 – May 29 | May 15 – Jun 5 | Jul 10 – Jul 24 |
| Cucumber | Apr 10 – Apr 17 | May 22 – May 29 | May 15 – Jun 5 | Jul 10 – Jul 24 |
| Carrot | — | — | Apr 17 – May 22 | Jul 10 – Jul 24 |
| Onion | Feb 13 – Feb 27 | Apr 10 – Apr 24 | — | — |
| Potato | — | Apr 10 – May 1 | — | — |
| Basil | Mar 27 – Apr 10 | May 22 – Jun 5 | May 22 – Jun 12 | — |
| Spinach | — | — | Mar 27 – Apr 24 | Aug 7 – Sep 4 |
| Kale | Mar 13 – Mar 27 | Apr 10 – May 1 | Apr 10 – May 1 | Jul 24 – Aug 21 |
| Broccoli | Mar 13 – Mar 27 | Apr 24 – May 15 | — | Jul 10 – Jul 24 |
| Peas | — | — | Mar 27 – Apr 17 | Jul 24 – Aug 7 |
| Eggplant | Feb 27 – Mar 13 | May 22 – Jun 5 | — | — |
| Cabbage | Mar 13 – Mar 27 | Apr 10 – Apr 24 | — | Jul 10 – Jul 24 |
| Radish | — | — | Apr 3 – May 22 | Aug 21 – Sep 18 |
| Strawberry | — | Apr 10 – May 1 | — | — |
| Beets | — | — | Apr 17 – May 29 | Jul 24 – Aug 7 |
Nearby cities in Colorado
- Arvada — zone 6a, last frost May 11, first frost Sep 29
- Westminster — zone 6a, last frost May 7, first frost Oct 4
- Denver — zone 6a, last frost May 8, first frost Oct 3
- Broomfield — zone 6a, last frost May 7, first frost Oct 4
- Centennial — zone 6a, last frost May 10, first frost Oct 3
- Thornton — zone 6a, last frost May 7, first frost Oct 4
More: all Colorado cities · other zone 6a cities: Chicago, IL, Denver, CO, Milwaukee, WI, Colorado Springs, CO, Omaha, NE, Aurora, CO, Lincoln, NE, Fort Wayne, IN
Lakewood gardening questions
When is the last frost in Lakewood, CO?
Plan around May 8. At NOAA's Lakewood, CO station, 3.5 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 May 3, and after May 18 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Apr 22. The 90% and 10% dates are 29 days apart, close to the 36-day median for cities on this site.
When should I plant tomatoes in Lakewood, CO?
Start seeds indoors Mar 13 – Mar 27 and set transplants outside May 15 – May 29, once nights stay above 50°F and the soil is near 60°F. That leaves 147 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 Lakewood?
About 155 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 133 days, and in 1 year in 10 it runs 175 days or more. In fall there is a 10% chance of frost by Sep 24 and a 30% chance by Oct 2. That ranks 9th longest of 16 Colorado cities on this site.
When should I plant a fall garden in Lakewood?
Count back from the first fall frost (Oct 2): transplant broccoli Jul 10 – Jul 24; sow kale Jul 24 – Aug 21; sow lettuce Jul 24 – Aug 21; sow radishes Aug 21 – Sep 18. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Oct 16. How the math works: succession and fall planting.
Did Lakewood's hardiness zone change on the 2023 map?
Yes. Most of Lakewood was zone 5b on the 2012 map and is zone 6a 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.
Is all of Lakewood in zone 6a?
No. Zone 6a covers about 92% of the city's land; the rest is in 5b (8%), measured across the city's 10 ZIP codes. Check your own ZIP code in the table above or with the ZIP lookup.