Frost dates for 80108 — Castle Rock, CO
Last spring frostMay 9median date
First fall frostOct 2median date
Growing season146 daysfrost-free
Hardiness zone5bZone 5b
How Castle Rock compares
- In 8 years out of 10, the last spring frost in Castle Rock falls between April 30 and May 24, a 24-day window. The first fall frost falls between September 17 and October 16.
- The median last frost is 2 days earlier than the Colorado median of May 11.
- Its 146-day growing season is longer than 50% of the 374 Colorado places with a regular frost season (state median 146 days).
- The last frost is 8 days later than the zone 5b median of May 1. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 5b chart.
- The weather station records an average of 167 nights a year at or below 32°F.
- Compared with Aurora, CO, 29 km away, the last frost here is 2 days later than there and the growing season is 8 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 30 |
| 50% (median) | May 9 |
| 10% (safe for tender plants) | May 24 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 17 |
| 50% (median) | October 2 |
| 90% (late) | October 16 |
Frost here means 32°F (0°C). A median date means half of years have their last frost earlier and half later.
Planting calendar for Castle Rock, CO
Frost dates for 80108 — Castle Rock, CO — last frost May 9, first frost Oct 2, zone 5b. whenisthelastfrost.com
Crop
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Start indoors: Feb 14 to Feb 28Transplant outside: Apr 11 to Apr 25
Start indoors: Feb 28 to Mar 14Transplant outside: May 23 to Jun 6
Start indoors: Feb 28 to Mar 14Transplant outside: May 23 to Jun 6
Start indoors: Mar 14 to Mar 28Transplant outside: May 16 to May 30
Start indoors: Mar 14 to Mar 28Transplant outside: Apr 18 to May 2Sow outdoors: Apr 11 to May 16Plant for fall: Aug 7 to Sep 4
Start indoors: Mar 14 to Mar 28Transplant outside: Apr 11 to Apr 25Sow outdoors: Apr 11 to Apr 25Plant for fall: Jul 24 to Aug 14
Start indoors: Mar 14 to Mar 28Transplant outside: Apr 25 to May 9Plant for fall: Jun 26 to Jul 17
Start indoors: Mar 14 to Mar 28Transplant outside: Apr 18 to May 2Plant for fall: Jun 26 to Jul 17
Start indoors: Mar 14 to Mar 28Transplant outside: Apr 25 to May 9Plant for fall: Jun 26 to Jul 17
Start indoors: Mar 28 to Apr 11Transplant outside: May 30 to Jun 13Sow outdoors: May 30 to Jun 13
Start indoors: Mar 28 to Apr 11Transplant outside: May 16 to May 30
Sow outdoors: Mar 28 to Apr 18Plant for fall: Jul 10 to Jul 31
Sow outdoors: Mar 28 to Apr 18Plant for fall: Aug 7 to Aug 28
Sow outdoors: Apr 4 to May 16Plant for fall: Aug 21 to Sep 11
Start indoors: Apr 11 to Apr 18Transplant outside: May 23 to May 30Sow outdoors: May 16 to May 30Plant for fall: Jul 17 to Jul 31
Start indoors: Apr 11 to Apr 18Sow outdoors: May 16 to May 30Plant for fall: Jul 24 to Aug 7
Start indoors: Apr 11 to Apr 18Sow outdoors: May 16 to May 30
Start indoors: Apr 11 to Apr 18Transplant outside: May 23 to Jun 6
Sow outdoors: Apr 18 to May 16Plant for fall: Jul 10 to Jul 24
Sow outdoors: Apr 18 to May 16Plant for fall: Jul 24 to Aug 7
Sow outdoors: Apr 18 to May 9
Sow outdoors: Apr 25 to May 23Plant for fall: Jul 24 to Aug 7
Sow outdoors: Apr 25 to May 16Plant for fall: Aug 7 to Aug 28
Sow outdoors: May 16 to Jun 6Plant for fall: Jul 17 to Jul 31
Sow outdoors: May 16 to May 30
Transplant outside: May 23 to Jun 13
Plant for fall: Sep 18 to Oct 23
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Castle Rock, CO
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 14 – Feb 28 | Apr 11 – Apr 25 | — | — |
| Peppers | Feb 28 – Mar 14 | May 23 – Jun 6 | — | — |
| Eggplant | Feb 28 – Mar 14 | May 23 – Jun 6 | — | — |
| Tomatoes | Mar 14 – Mar 28 | May 16 – May 30 | — | — |
| Lettuce | Mar 14 – Mar 28 | Apr 18 – May 2 | Apr 11 – May 16 | Aug 7 – Sep 4 |
| Kale | Mar 14 – Mar 28 | Apr 11 – Apr 25 | Apr 11 – Apr 25 | Jul 24 – Aug 14 |
| Broccoli | Mar 14 – Mar 28 | Apr 25 – May 9 | — | Jun 26 – Jul 17 |
| Cabbage | Mar 14 – Mar 28 | Apr 18 – May 2 | — | Jun 26 – Jul 17 |
| Cauliflower | Mar 14 – Mar 28 | Apr 25 – May 9 | — | Jun 26 – Jul 17 |
| Okra | Mar 28 – Apr 11 | May 30 – Jun 13 | May 30 – Jun 13 | — |
| Basil | Mar 28 – Apr 11 | May 16 – May 30 | — | — |
| Peas | — | — | Mar 28 – Apr 18 | Jul 10 – Jul 31 |
| Spinach | — | — | Mar 28 – Apr 18 | Aug 7 – Aug 28 |
| Radishes | — | — | Apr 4 – May 16 | Aug 21 – Sep 11 |
| Cucumbers | Apr 11 – Apr 18 | May 23 – May 30 | May 16 – May 30 | Jul 17 – Jul 31 |
| Zucchini & Summer Squash | Apr 11 – Apr 18 | — | May 16 – May 30 | Jul 24 – Aug 7 |
| Winter Squash & Pumpkins | Apr 11 – Apr 18 | — | May 16 – May 30 | — |
| Melons & Watermelon | Apr 11 – Apr 18 | May 23 – Jun 6 | — | — |
| Carrots | — | — | Apr 18 – May 16 | Jul 10 – Jul 24 |
| Beets | — | — | Apr 18 – May 16 | Jul 24 – Aug 7 |
| Potatoes | — | — | Apr 18 – May 9 | — |
| Swiss Chard | — | — | Apr 25 – May 23 | Jul 24 – Aug 7 |
| Cilantro | — | — | Apr 25 – May 16 | Aug 7 – Aug 28 |
| Green Beans | — | — | May 16 – Jun 6 | Jul 17 – Jul 31 |
| Sweet Corn | — | — | May 16 – May 30 | — |
| Sweet Potatoes | — | May 23 – Jun 13 | — | — |
| Garlic | — | — | — | Sep 18 – Oct 23 |
Dates come from the median frost dates and common extension-service timing. Adjust for your soil temperature, microclimate and the varieties you grow.
About these dates
Based on 1991–2020 NOAA climate normals for the Castle Rock, CO weather station, 6 km away (elevation 6,184 ft (1,885 m)).
ZIP codes in Castle Rock: 80104 80108 80109
Frost dates near Castle Rock
- Parker May 9 · Oct 3
- Lone Tree May 5 · Oct 8
- Franktown May 16 · Oct 2
- Louviers May 16 · Oct 1
- Littleton May 2 · Oct 11
- Englewood May 2 · Oct 11
- Elizabeth May 16 · Oct 2
- Sedalia May 16 · Oct 1
Frequently asked questions
When is the last frost in Castle Rock, CO?
The median last spring frost in Castle Rock, CO is May 9. There is still about a 10% chance of frost after May 24, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Castle Rock, CO?
The median first fall frost is October 2, with about a 10% chance of frost before September 17.
How long is the growing season in Castle Rock, CO?
About 146 days between the median last spring frost and first fall frost.
What planting zone is Castle Rock, CO?
Castle Rock, CO is in USDA hardiness zone 5b.