Granby, CO frost dates
Last spring frostJun 13median date
First fall frostSep 7median date
Growing season86 daysfrost-free
Hardiness zone5aZone 5a
How Granby compares
- In 8 years out of 10, the last spring frost in Granby falls between June 1 and June 28, a 27-day window. The first fall frost falls between August 21 and September 21.
- The median last frost is 33 days later than the Colorado median of May 11.
- Its 86-day growing season is longer than 6% of the 374 Colorado places with a regular frost season (state median 146 days).
- The last frost is 41 days later than the zone 5a median of May 3. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 5a chart.
- The weather station records an average of 245 nights a year at or below 32°F.
- Compared with Boulder, CO, 53 km away, the last frost here is 38 days later than there and the growing season is 66 days shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | June 1 |
| 50% (median) | June 13 |
| 10% (safe for tender plants) | June 28 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | August 21 |
| 50% (median) | September 7 |
| 90% (late) | September 21 |
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 Granby, CO
Granby, CO frost dates — last frost Jun 13, first frost Sep 7, zone 5a. whenisthelastfrost.com
Crop
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Start indoors: Mar 21 to Apr 4Transplant outside: May 16 to May 30
Start indoors: Apr 4 to Apr 18Transplant outside: Jun 27 to Jul 11
Start indoors: Apr 4 to Apr 18Transplant outside: Jun 27 to Jul 11
Start indoors: Apr 18 to May 2Transplant outside: Jun 20 to Jul 4
Start indoors: Apr 18 to May 2Transplant outside: May 23 to Jun 6Sow outdoors: May 16 to Jun 20Plant for fall: Jul 13 to Aug 10
Start indoors: Apr 18 to May 2Transplant outside: May 16 to May 30Sow outdoors: May 16 to May 30Plant for fall: Jun 29 to Jul 20
Start indoors: Apr 18 to May 2Transplant outside: May 30 to Jun 13
Start indoors: Apr 18 to May 2Transplant outside: May 23 to Jun 6
Start indoors: Apr 18 to May 2Transplant outside: May 30 to Jun 13
Start indoors: May 2 to May 16Transplant outside: Jul 4 to Jul 18Sow outdoors: Jul 4 to Jul 18
Start indoors: May 2 to May 16Transplant outside: Jun 20 to Jul 4
Sow outdoors: May 2 to May 23
Sow outdoors: May 2 to May 23Plant for fall: Jul 13 to Aug 3
Sow outdoors: May 9 to Jun 20Plant for fall: Jul 27 to Aug 17
Start indoors: May 16 to May 23Transplant outside: Jun 27 to Jul 4Sow outdoors: Jun 20 to Jul 4
Start indoors: May 16 to May 23Sow outdoors: Jun 20 to Jul 4
Start indoors: May 16 to May 23Sow outdoors: Jun 20 to Jul 4
Start indoors: May 16 to May 23Transplant outside: Jun 27 to Jul 11
Sow outdoors: May 23 to Jun 20
Sow outdoors: May 23 to Jun 20
Sow outdoors: May 23 to Jun 13
Sow outdoors: May 30 to Jun 27
Sow outdoors: May 30 to Jun 20Plant for fall: Jul 13 to Aug 3
Sow outdoors: Jun 20 to Jul 11
Sow outdoors: Jun 20 to Jul 4
Transplant outside: Jun 27 to Jul 18
Plant for fall: Aug 24 to Sep 28
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Granby, CO
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Mar 21 – Apr 4 | May 16 – May 30 | — | — |
| Peppers Warning: Your frost-free season is about 86 days, which is tight for peppers (75+ days). Choose early varieties and use transplants or row covers. | Apr 4 – Apr 18 | Jun 27 – Jul 11 | — | — |
| Eggplant Warning: Your frost-free season is about 86 days, which is tight for eggplant (75+ days). Choose early varieties and use transplants or row covers. | Apr 4 – Apr 18 | Jun 27 – Jul 11 | — | — |
| Tomatoes | Apr 18 – May 2 | Jun 20 – Jul 4 | — | — |
| Lettuce | Apr 18 – May 2 | May 23 – Jun 6 | May 16 – Jun 20 | Jul 13 – Aug 10 |
| Kale | Apr 18 – May 2 | May 16 – May 30 | May 16 – May 30 | Jun 29 – Jul 20 |
| Broccoli | Apr 18 – May 2 | May 30 – Jun 13 | — | — |
| Cabbage | Apr 18 – May 2 | May 23 – Jun 6 | — | — |
| Cauliflower | Apr 18 – May 2 | May 30 – Jun 13 | — | — |
| Okra | May 2 – May 16 | Jul 4 – Jul 18 | Jul 4 – Jul 18 | — |
| Basil | May 2 – May 16 | Jun 20 – Jul 4 | — | — |
| Peas | — | — | May 2 – May 23 | — |
| Spinach | — | — | May 2 – May 23 | Jul 13 – Aug 3 |
| Radishes | — | — | May 9 – Jun 20 | Jul 27 – Aug 17 |
| Cucumbers | May 16 – May 23 | Jun 27 – Jul 4 | Jun 20 – Jul 4 | — |
| Zucchini & Summer Squash | May 16 – May 23 | — | Jun 20 – Jul 4 | — |
| Winter Squash & Pumpkins Warning: Your frost-free season is about 86 days, which is tight for winter squash & pumpkins (100+ days). Choose early varieties and use transplants or row covers. | May 16 – May 23 | — | Jun 20 – Jul 4 | — |
| Melons & Watermelon Warning: Your frost-free season is about 86 days, which is tight for melons & watermelon (85+ days). Choose early varieties and use transplants or row covers. | May 16 – May 23 | Jun 27 – Jul 11 | — | — |
| Carrots | — | — | May 23 – Jun 20 | — |
| Beets | — | — | May 23 – Jun 20 | — |
| Potatoes | — | — | May 23 – Jun 13 | — |
| Swiss Chard | — | — | May 30 – Jun 27 | — |
| Cilantro | — | — | May 30 – Jun 20 | Jul 13 – Aug 3 |
| Green Beans | — | — | Jun 20 – Jul 11 | — |
| Sweet Corn Warning: Your frost-free season is about 86 days, which is tight for sweet corn (80+ days). Choose early varieties and use transplants or row covers. | — | — | Jun 20 – Jul 4 | — |
| Sweet Potatoes Warning: Your frost-free season is about 86 days, which is tight for sweet potatoes (100+ days). Choose early varieties and use transplants or row covers. | — | Jun 27 – Jul 18 | — | — |
| Garlic | — | — | — | Aug 24 – Sep 28 |
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 Grand Lake 6 Ssw, CO weather station, 13 km away (elevation 8,287 ft (2,526 m)).
Frost dates near Granby
- Tabernash frost any month
- Hot Sulphur Springs Jun 12 · Sep 10
- Fraser frost any month
- Grand Lake frost any month
- Parshall Jun 12 · Sep 10
- Winter Park frost any month
- Ward Jun 21 · Sep 2
- Allenspark Jun 14 · Sep 12
- Kremmling Jun 14 · Sep 5
- Nederland Jun 21 · Sep 2
Frequently asked questions
When is the last frost in Granby, CO?
The median last spring frost in Granby, CO is June 13. There is still about a 10% chance of frost after June 28, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Granby, CO?
The median first fall frost is September 7, with about a 10% chance of frost before August 21.
How long is the growing season in Granby, CO?
About 86 days between the median last spring frost and first fall frost.
What planting zone is Granby, CO?
Granby, CO is in USDA hardiness zone 5a.