Morrison, CO frost dates
Last spring frostMay 2median date
First fall frostOct 11median date
Growing season162 daysfrost-free
Hardiness zone5bZone 5b
How Morrison compares
- In 8 years out of 10, the last spring frost in Morrison falls between April 20 and May 17, a 27-day window. The first fall frost falls between September 27 and October 23.
- The median last frost is 9 days earlier than the Colorado median of May 11.
- Its 162-day growing season is longer than 85% of the 374 Colorado places with a regular frost season (state median 146 days).
- The last frost is typical for zone 5b, where the median is May 1.
- The weather station records an average of 147 nights a year at or below 32°F.
- Compared with Denver, CO, 22 km away, the last frost here is 2 days later than there and the growing season is 3 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | April 20 |
| 50% (median) | May 2 |
| 10% (safe for tender plants) | May 17 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | September 27 |
| 50% (median) | October 11 |
| 90% (late) | October 23 |
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 Morrison, CO
Morrison, CO frost dates — last frost May 2, first frost Oct 11, zone 5b. whenisthelastfrost.com
Crop
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Start indoors: Feb 7 to Feb 21Transplant outside: Apr 4 to Apr 18
Start indoors: Feb 21 to Mar 7Transplant outside: May 16 to May 30
Start indoors: Feb 21 to Mar 7Transplant outside: May 16 to May 30
Start indoors: Mar 7 to Mar 21Transplant outside: May 9 to May 23
Start indoors: Mar 7 to Mar 21Transplant outside: Apr 11 to Apr 25Sow outdoors: Apr 4 to May 9Plant for fall: Aug 16 to Sep 13
Start indoors: Mar 7 to Mar 21Transplant outside: Apr 4 to Apr 18Sow outdoors: Apr 4 to Apr 18Plant for fall: Aug 2 to Aug 23
Start indoors: Mar 7 to Mar 21Transplant outside: Apr 18 to May 2Plant for fall: Jul 5 to Jul 26
Start indoors: Mar 7 to Mar 21Transplant outside: Apr 11 to Apr 25Plant for fall: Jul 5 to Jul 26
Start indoors: Mar 7 to Mar 21Transplant outside: Apr 18 to May 2Plant for fall: Jul 5 to Jul 26
Start indoors: Mar 21 to Apr 4Transplant outside: May 23 to Jun 6Sow outdoors: May 23 to Jun 6
Start indoors: Mar 21 to Apr 4Transplant outside: May 9 to May 23
Sow outdoors: Mar 21 to Apr 11Plant for fall: Jul 19 to Aug 9
Sow outdoors: Mar 21 to Apr 11Plant for fall: Aug 16 to Sep 6
Sow outdoors: Mar 28 to May 9Plant for fall: Aug 30 to Sep 20
Start indoors: Apr 4 to Apr 11Transplant outside: May 16 to May 23Sow outdoors: May 9 to May 23Plant for fall: Jul 26 to Aug 9
Start indoors: Apr 4 to Apr 11Sow outdoors: May 9 to May 23Plant for fall: Aug 2 to Aug 16
Start indoors: Apr 4 to Apr 11Sow outdoors: May 9 to May 23
Start indoors: Apr 4 to Apr 11Transplant outside: May 16 to May 30
Sow outdoors: Apr 11 to May 9Plant for fall: Jul 19 to Aug 2
Sow outdoors: Apr 11 to May 9Plant for fall: Aug 2 to Aug 16
Sow outdoors: Apr 11 to May 2
Sow outdoors: Apr 18 to May 16Plant for fall: Aug 2 to Aug 16
Sow outdoors: Apr 18 to May 9Plant for fall: Aug 16 to Sep 6
Sow outdoors: May 9 to May 30Plant for fall: Jul 26 to Aug 9
Sow outdoors: May 9 to May 23
Transplant outside: May 16 to Jun 6
Plant for fall: Sep 27 to Nov 1
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Morrison, CO
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Feb 7 – Feb 21 | Apr 4 – Apr 18 | — | — |
| Peppers | Feb 21 – Mar 7 | May 16 – May 30 | — | — |
| Eggplant | Feb 21 – Mar 7 | May 16 – May 30 | — | — |
| Tomatoes | Mar 7 – Mar 21 | May 9 – May 23 | — | — |
| Lettuce | Mar 7 – Mar 21 | Apr 11 – Apr 25 | Apr 4 – May 9 | Aug 16 – Sep 13 |
| Kale | Mar 7 – Mar 21 | Apr 4 – Apr 18 | Apr 4 – Apr 18 | Aug 2 – Aug 23 |
| Broccoli | Mar 7 – Mar 21 | Apr 18 – May 2 | — | Jul 5 – Jul 26 |
| Cabbage | Mar 7 – Mar 21 | Apr 11 – Apr 25 | — | Jul 5 – Jul 26 |
| Cauliflower | Mar 7 – Mar 21 | Apr 18 – May 2 | — | Jul 5 – Jul 26 |
| Okra | Mar 21 – Apr 4 | May 23 – Jun 6 | May 23 – Jun 6 | — |
| Basil | Mar 21 – Apr 4 | May 9 – May 23 | — | — |
| Peas | — | — | Mar 21 – Apr 11 | Jul 19 – Aug 9 |
| Spinach | — | — | Mar 21 – Apr 11 | Aug 16 – Sep 6 |
| Radishes | — | — | Mar 28 – May 9 | Aug 30 – Sep 20 |
| Cucumbers | Apr 4 – Apr 11 | May 16 – May 23 | May 9 – May 23 | Jul 26 – Aug 9 |
| Zucchini & Summer Squash | Apr 4 – Apr 11 | — | May 9 – May 23 | Aug 2 – Aug 16 |
| Winter Squash & Pumpkins | Apr 4 – Apr 11 | — | May 9 – May 23 | — |
| Melons & Watermelon | Apr 4 – Apr 11 | May 16 – May 30 | — | — |
| Carrots | — | — | Apr 11 – May 9 | Jul 19 – Aug 2 |
| Beets | — | — | Apr 11 – May 9 | Aug 2 – Aug 16 |
| Potatoes | — | — | Apr 11 – May 2 | — |
| Swiss Chard | — | — | Apr 18 – May 16 | Aug 2 – Aug 16 |
| Cilantro | — | — | Apr 18 – May 9 | Aug 16 – Sep 6 |
| Green Beans | — | — | May 9 – May 30 | Jul 26 – Aug 9 |
| Sweet Corn | — | — | May 9 – May 23 | — |
| Sweet Potatoes | — | May 16 – Jun 6 | — | — |
| Garlic | — | — | — | Sep 27 – Nov 1 |
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 Marston Fltr Plt, CO weather station, 9 km away (elevation 5,610 ft (1,710 m)).
Frost dates near Morrison
- Indian Hills May 23 · Sep 22
- Idledale May 23 · Sep 22
- Kittredge May 23 · Sep 22
- Evergreen May 23 · Sep 22
- Golden May 3 · Oct 7
- Littleton May 2 · Oct 11
- Conifer May 23 · Sep 22
- Englewood May 2 · Oct 11
- Wheat Ridge May 5 · Oct 5
- Louviers May 16 · Oct 1
Frequently asked questions
When is the last frost in Morrison, CO?
The median last spring frost in Morrison, CO is May 2. There is still about a 10% chance of frost after May 17, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Morrison, CO?
The median first fall frost is October 11, with about a 10% chance of frost before September 27.
How long is the growing season in Morrison, CO?
About 162 days between the median last spring frost and first fall frost.
What planting zone is Morrison, CO?
Morrison, CO is in USDA hardiness zone 5b.