Arvada, Colorado: planting zone & frost dates
Arvada 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 11 and the first fall frost around Sep 29.
Frost dates
| Probability | Last spring frost (32°F) | First fall frost (32°F) |
|---|---|---|
| Safer (10% risk) | May 18 | Sep 20 |
| Typical planning date (30% risk) | May 11 | Sep 29 |
| Median (50%) | May 5 | Oct 5 |
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 WHEAT RIDGE 2, CO (USC00058995), 4.4 mi (7.1 km) from the city center and 108 ft lower than the city center (-33 m). Record used for the 1991–2020 normals: 28 years.
Why your yard may differ from the station: microclimates.
Hardiness zone across Arvada
Arvada spans more than one half-zone. Share of the city's land area by zone (via its 6 ZIP codes): 6a (85%), 5b (15%). The headline zone is the one covering the most land. Look up your ZIP for your exact zone.
Vegetable planting calendar for Arvada
Dates are counted from the 30%-risk frost dates above (last frost May 11, first frost Sep 29). 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 16 – Mar 30 | May 18 – Jun 1 | — | — |
| Pepper | Mar 2 – Mar 16 | May 25 – Jun 8 | — | — |
| Lettuce | Mar 30 – Apr 13 | Apr 27 – May 18 | Apr 13 – May 25 | Jul 21 – Aug 18 |
| Green Beans | — | — | May 18 – Jun 22 | Jul 7 – Jul 21 |
| Sweet Corn | — | — | May 18 – Jun 15 | — |
| Zucchini & Summer Squash | Apr 13 – Apr 20 | May 18 – Jun 1 | May 18 – Jun 8 | Jul 7 – Jul 21 |
| Cucumber | Apr 13 – Apr 20 | May 25 – Jun 1 | May 18 – Jun 8 | Jul 7 – Jul 21 |
| Carrot | — | — | Apr 20 – May 25 | Jul 7 – Jul 21 |
| Onion | Feb 16 – Mar 2 | Apr 13 – Apr 27 | — | — |
| Potato | — | Apr 13 – May 4 | — | — |
| Basil | Mar 30 – Apr 13 | May 25 – Jun 8 | May 25 – Jun 15 | — |
| Spinach | — | — | Mar 30 – Apr 27 | Aug 4 – Sep 1 |
| Kale | Mar 16 – Mar 30 | Apr 13 – May 4 | Apr 13 – May 4 | Jul 21 – Aug 18 |
| Broccoli | Mar 16 – Mar 30 | Apr 27 – May 18 | — | Jul 7 – Jul 21 |
| Peas | — | — | Mar 30 – Apr 20 | Jul 21 – Aug 4 |
| Eggplant | Mar 2 – Mar 16 | May 25 – Jun 8 | — | — |
| Cabbage | Mar 16 – Mar 30 | Apr 13 – Apr 27 | — | Jul 7 – Jul 21 |
| Radish | — | — | Apr 6 – May 25 | Aug 18 – Sep 15 |
| Strawberry | — | Apr 13 – May 4 | — | — |
| Beets | — | — | Apr 20 – Jun 1 | Jul 21 – Aug 4 |
Nearby cities in Colorado
- 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
- Boulder — zone 6a, last frost May 11, first frost Sep 30
- Thornton — zone 6a, last frost May 7, first frost Oct 4
- Denver — zone 6a, last frost May 8, first frost Oct 3
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
Arvada gardening questions
When is the last frost in Arvada, CO?
Plan around May 11. At NOAA's Wheat Ridge 2, CO station, 4.4 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 May 5, and after May 18 the risk drops to about 1 in 10. A hard freeze (28°F) usually ends earlier, around Apr 25. The last frost is fairly predictable here: only 24 days separate the 90% and 10% dates (median for cities on this site: 36 days).
When should I plant tomatoes in Arvada, CO?
Start seeds indoors Mar 16 – Mar 30 and set transplants outside May 18 – Jun 1, once nights stay above 50°F and the soil is near 60°F. That leaves 141 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 Arvada?
About 151 days without a 32°F frost in a typical (median) year. In 9 years out of 10 the season lasts at least 132 days, and in 1 year in 10 it runs 167 days or more. In fall there is a 10% chance of frost by Sep 20 and a 30% chance by Sep 29. That ranks 12th longest of 16 Colorado cities on this site.
When should I plant a fall garden in Arvada?
Count back from the first fall frost (Sep 29): transplant broccoli Jul 7 – Jul 21; sow kale Jul 21 – Aug 18; sow lettuce Jul 21 – Aug 18; sow radishes Aug 18 – Sep 15. Hardy crops keep growing through light frosts; the median 28°F hard freeze here is Oct 14. How the math works: succession and fall planting.
Did Arvada's hardiness zone change on the 2023 map?
No. Going by the zone that covers most of the city's land, Arvada is zone 6a on both the 2012 and the 2023 USDA maps (PRISM/OSU ZIP listings). About 42% of U.S. ZIP codes kept their half-zone in 2023. Why the 2023 map is warmer.
Is all of Arvada in zone 6a?
No. Zone 6a covers about 85% of the city's land; the rest is in 5b (15%), measured across the city's 6 ZIP codes. Check your own ZIP code in the table above or with the ZIP lookup.