Frost dates for Mt Hamilton, CA
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 3
typical year
Safe to plant
June 5
frost is over in 9 of 10 years
First fall frost
November 18
typical year
Growing season
197 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 5 – 19 | – |
| Spinach | – | Mar 22 – Apr 12 | Sep 23 – Oct 7 |
| Lettuce | – | Apr 5 – 26 | Sep 23 – Oct 7 |
| Radishes | – | Apr 5 – May 17 | Oct 7 – 21 |
| Onions | – | Apr 5 – 19 | – |
| Potatoes | – | Apr 12 – 26 | – |
| Carrots | – | Apr 12 – May 3 | Aug 26 – Sep 9 |
| Beets | – | Apr 5 – 19 | Sep 9 – 23 |
| Kale | Feb 22 – Mar 8 | Apr 5 – 19 | Sep 9 – 23 |
| Broccoli | Feb 22 – Mar 8 | Apr 19 – May 3 | Sep 9 – 23 |
| Cabbage | Feb 8 – 22 | Apr 5 – 19 | Sep 9 – 23 |
| Garlic | – | – | Oct 7 – 28 |
| Warm-season crops | |||
| Tomatoes | Apr 10 – 24 | Jun 5 – 19 | – |
| Peppers | Apr 3 – 17 | Jun 12 – 26 | – |
| Cucumbers | – | Jun 5 – 26 | – |
| Zucchini | – | Jun 5 – Jul 3 | – |
| Pumpkins | – | Jun 5 – 26 | – |
| Green beans | – | Jun 5 – Sep 9 | – |
| Sweet corn | – | Jun 5 – Jul 3 | – |
| Basil | May 1 – 15 | Jun 12 – 19 | – |
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 | June 5 | May 3 | April 7 |
| Fall frost before | October 22 | November 18 | December 12 |
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 10 (May 6 in a late year), and the first one in fall around December 7.
Where these dates come from
NOAA weather station MT HAMILTON, CA US (USC00045933), 1991–2020 climate normals. It's the nearest station for 6 zip codes, all within 13 miles:
94550, 95013, 95135, 95138, 95139, 95140
Planting dates follow common university extension advice; your local extension service can fine-tune them for your soil and microclimate.