Frost dates for Boulder, UT
When the last spring frost and first fall frost usually come, and when to plant, from 30 years of NOAA weather records.
Last spring frost
May 4
typical year
Safe to plant
May 25
frost is over in 9 of 10 years
First fall frost
October 14
typical year
Growing season
160 days
frost-free, typical year
Frost watch this week
Tonight's and the next six nights' lows from the National Weather Service forecast for the station's location. Frost: 32°F or colder. Possible frost: 33–36°F, mostly in low spots on clear, still nights.
When to plant
Counted from this page's frost dates. Warm-season crops wait for the safe-to-plant date.
| Crop | Start indoors | Plant outside | Fall planting |
|---|---|---|---|
| Cool-season crops | |||
| Peas | – | Apr 6 – 20 | – |
| Spinach | – | Mar 23 – Apr 13 | Aug 19 – Sep 2 |
| Lettuce | – | Apr 6 – 27 | Aug 19 – Sep 2 |
| Radishes | – | Apr 6 – May 18 | Sep 2 – 16 |
| Onions | – | Apr 6 – 20 | – |
| Potatoes | – | Apr 13 – 27 | – |
| Carrots | – | Apr 13 – May 4 | Jul 22 – Aug 5 |
| Beets | – | Apr 6 – 20 | Aug 5 – 19 |
| Kale | Feb 23 – Mar 9 | Apr 6 – 20 | Aug 5 – 19 |
| Broccoli | Feb 23 – Mar 9 | Apr 20 – May 4 | Aug 5 – 19 |
| Cabbage | Feb 9 – 23 | Apr 6 – 20 | Aug 5 – 19 |
| Garlic | – | – | Sep 2 – 23 |
| Warm-season crops | |||
| Tomatoes | Mar 30 – Apr 13 | May 25 – Jun 8 | – |
| Peppers | Mar 23 – Apr 6 | Jun 1 – 15 | – |
| Cucumbers | – | May 25 – Jun 15 | – |
| Zucchini | – | May 25 – Jun 22 | – |
| Pumpkins | – | May 25 – Jun 15 | – |
| Green beans | – | May 25 – Aug 5 | – |
| Sweet corn | – | May 25 – Jun 22 | – |
| Basil | Apr 20 – May 4 | Jun 1 – 8 | – |
Onions: from sets. Green beans: until 10 weeks before the first fall frost. Garlic: harvest next summer.
The year at a glance
Start indoors Plant outside Fall planting
The chance of frost, by date
| 1 year in 10 | Half of years | 9 years in 10 | |
|---|---|---|---|
| Spring frost after | May 25 | May 4 | April 20 |
| Fall frost before | September 30 | October 14 | October 29 |
Frost here means 32°F or colder. Read across: in 1 year in 10, spring frost carries on past the first date, which is why that date is the safe-to-plant date.
Hard freeze (28°F)
A hard freeze kills most garden plants, even hardy ones. The last one in spring usually comes around April 23 (May 12 in a late year), and the first one in fall around October 23.
Towns that use these dates
This is the nearest NOAA station with frost records for 1 town.
Boulder
Where these dates come from
NOAA weather station BOULDER, UT US (USC00420849), 1991–2020 climate normals. It's the nearest station for 1 zip code, all within 3 miles:
84716
Planting dates follow common university extension advice; your local extension service can fine-tune them for your soil and microclimate.