Denver, Colorado: planting zone & frost dates
Denver 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 3.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | May 16 | Sep 25 |
| Typical planning date (30% risk) | May 8 | Oct 3 |
| Median (50%) | May 4 | Oct 8 |
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 DENVER-STAPLETON, CO (USW00023062), 0.6 mi (1.0 km) from the city center and 7 ft lower than the city center (-2 m). Record used for the 1991–2020 normals: 28 years.
Hardiness zone across Denver
All 30 ZIP codes covering Denver are in zone 6a.
ZIP codes in Denver and their zones
| ZIP | Zone | Share of city land |
|---|---|---|
| 80249 | 6a | 31.1% |
| 80239 | 6a | 5.4% |
| 80216 | 6a | 4.8% |
| 80219 | 6a | 4.8% |
| 80238 | 6a | 4.4% |
| 80210 | 6a | 4.0% |
| 80204 | 6a | 3.6% |
| 80223 | 6a | 3.5% |
| 80220 | 6a | 3.4% |
| 80205 | 6a | 3.0% |
| 80211 | 6a | 2.9% |
| 80207 | 6a | 2.6% |
| 80237 | 6a | 2.4% |
| 80209 | 6a | 2.3% |
| 80222 | 6a | 2.1% |
| 80224 | 6a | 2.1% |
| 80236 | 6a | 2.0% |
| 80231 | 6a | 1.9% |
| 80212 | 6a | 1.7% |
| 80206 | 6a | 1.6% |
| 80230 | 6a | 1.6% |
| 80123 | 6a | 1.5% |
| 80218 | 6a | 1.0% |
| 80227 | 6a | 1.0% |
| 80247 | 6a | 1.0% |
| 80202 | 6a | 0.8% |
| 80203 | 6a | 0.7% |
| 80246 | 6a | 0.7% |
| 80266 | 6a | 0.1% |
| 80290 | 6a | 0.0% |
Vegetable planting calendar for Denver
Dates are counted from the 30%-risk frost dates above (last frost May 8, first frost Oct 3). 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 25 – Aug 22 |
| Green Beans | — | — | May 15 – Jun 19 | Jul 11 – Jul 25 |
| Sweet Corn | — | — | May 15 – Jun 12 | — |
| Zucchini & Summer Squash | Apr 10 – Apr 17 | May 15 – May 29 | May 15 – Jun 5 | Jul 11 – Jul 25 |
| Cucumber | Apr 10 – Apr 17 | May 22 – May 29 | May 15 – Jun 5 | Jul 11 – Jul 25 |
| Carrot | — | — | Apr 17 – May 22 | Jul 11 – Jul 25 |
| 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 8 – Sep 5 |
| Kale | Mar 13 – Mar 27 | Apr 10 – May 1 | Apr 10 – May 1 | Jul 25 – Aug 22 |
| Broccoli | Mar 13 – Mar 27 | Apr 24 – May 15 | — | Jul 11 – Jul 25 |
| Peas | — | — | Mar 27 – Apr 17 | Jul 25 – Aug 8 |
| Eggplant | Feb 27 – Mar 13 | May 22 – Jun 5 | — | — |
| Cabbage | Mar 13 – Mar 27 | Apr 10 – Apr 24 | — | Jul 11 – Jul 25 |
| Radish | — | — | Apr 3 – May 22 | Aug 22 – Sep 19 |
| Strawberry | — | Apr 10 – May 1 | — | — |
| Beets | — | — | Apr 17 – May 29 | Jul 25 – Aug 8 |
Nearby cities in Colorado
- Aurora — zone 6a, last frost May 12, first frost Oct 2
- Thornton — zone 6a, last frost May 7, first frost Oct 4
- Centennial — zone 6a, last frost May 10, first frost Oct 3
- Westminster — zone 6a, last frost May 7, first frost Oct 4
- Lakewood — zone 6a, last frost May 8, first frost Oct 2
- Broomfield — zone 6a, last frost May 7, first frost Oct 4
More: all Colorado cities · other zone 6a cities: Chicago, IL, Milwaukee, WI, Colorado Springs, CO, Omaha, NE, Aurora, CO, Lincoln, NE, Fort Wayne, IN, Worcester, MA