Diablo, CA frost dates
Last spring frostMar 8median date
First fall frostDec 22median date
Growing season289 daysfrost-free
Hardiness zone9bZone 9b
How Diablo compares
- In 8 years out of 10, the last spring frost in Diablo falls between January 12 and April 15, a 93-day window. The first fall frost falls between November 23 and February 11.
- The median last frost is 23 days earlier than the California median of Mar 31.
- Its 289-day growing season is longer than 90% of the 636 California places with a regular frost season (state median 235 days).
- The last frost is 16 days later than the zone 9b median of Feb 20. Hardiness zones measure winter cold, not season length, so use these dates rather than a zone 9b chart.
- The weather station records an average of 19 nights a year at or below 32°F.
- Compared with San Ramon, CA, 9 km away, the last frost here is 21 days later than there and the growing season is 1 day shorter.
Frost probability
| Chance of frost after | Date |
|---|---|
| 90% (early) | January 12 |
| 50% (median) | March 8 |
| 10% (safe for tender plants) | April 15 |
| Chance of frost before | Date |
|---|---|
| 10% (early) | November 23 |
| 50% (median) | December 22 |
| 90% (late) | February 11 |
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 Diablo, CA
Diablo, CA frost dates — last frost Mar 8, first frost Dec 22, zone 9b. whenisthelastfrost.com
Crop
JFMAMJJASOND
Start indoors: Dec 14 to Dec 28Transplant outside: Feb 8 to Feb 22
Start indoors: Dec 28 to Jan 11Start indoors: Dec 28 to Jan 11Transplant outside: Mar 22 to Apr 5
Start indoors: Dec 28 to Jan 11Start indoors: Dec 28 to Jan 11Transplant outside: Mar 22 to Apr 5
Start indoors: Jan 11 to Jan 25Transplant outside: Mar 15 to Mar 29
Start indoors: Jan 11 to Jan 25Transplant outside: Feb 15 to Mar 1Sow outdoors: Feb 8 to Mar 15Plant for fall: Oct 27 to Nov 24
Start indoors: Jan 11 to Jan 25Transplant outside: Feb 8 to Feb 22Sow outdoors: Feb 8 to Feb 22Plant for fall: Oct 13 to Nov 3
Start indoors: Jan 11 to Jan 25Transplant outside: Feb 22 to Mar 8Plant for fall: Sep 15 to Oct 6
Start indoors: Jan 11 to Jan 25Transplant outside: Feb 15 to Mar 1Plant for fall: Sep 15 to Oct 6
Start indoors: Jan 11 to Jan 25Transplant outside: Feb 22 to Mar 8Plant for fall: Sep 15 to Oct 6
Start indoors: Jan 25 to Feb 8Transplant outside: Mar 29 to Apr 12Sow outdoors: Mar 29 to Apr 12
Start indoors: Jan 25 to Feb 8Transplant outside: Mar 15 to Mar 29
Sow outdoors: Jan 25 to Feb 15Plant for fall: Sep 29 to Oct 20
Sow outdoors: Jan 25 to Feb 15Plant for fall: Oct 27 to Nov 17
Sow outdoors: Feb 1 to Mar 15Plant for fall: Nov 10 to Dec 1
Start indoors: Feb 8 to Feb 15Transplant outside: Mar 22 to Mar 29Sow outdoors: Mar 15 to Mar 29Plant for fall: Oct 6 to Oct 20
Start indoors: Feb 8 to Feb 15Sow outdoors: Mar 15 to Mar 29Plant for fall: Oct 13 to Oct 27
Start indoors: Feb 8 to Feb 15Sow outdoors: Mar 15 to Mar 29
Start indoors: Feb 8 to Feb 15Transplant outside: Mar 22 to Apr 5
Sow outdoors: Feb 15 to Mar 15Plant for fall: Sep 29 to Oct 13
Sow outdoors: Feb 15 to Mar 15Plant for fall: Oct 13 to Oct 27
Sow outdoors: Feb 15 to Mar 8
Sow outdoors: Feb 22 to Mar 22Plant for fall: Oct 13 to Oct 27
Sow outdoors: Feb 22 to Mar 15Plant for fall: Oct 27 to Nov 17
Sow outdoors: Mar 15 to Apr 5Plant for fall: Oct 6 to Oct 20
Sow outdoors: Mar 15 to Mar 29
Transplant outside: Mar 22 to Apr 12
Plant for fall: Dec 8 to Jan 12Plant for fall: Dec 8 to Jan 12
Start indoorsTransplant outsideSow outdoorsPlant for fallMedian frost dates
When to plant vegetables in Diablo, CA
| Crop | Start indoors | Transplant | Sow outdoors | Fall crop |
|---|---|---|---|---|
| Onions | Dec 14 – Dec 28 | Feb 8 – Feb 22 | — | — |
| Peppers | Dec 28 – Jan 11 | Mar 22 – Apr 5 | — | — |
| Eggplant | Dec 28 – Jan 11 | Mar 22 – Apr 5 | — | — |
| Tomatoes | Jan 11 – Jan 25 | Mar 15 – Mar 29 | — | — |
| Lettuce | Jan 11 – Jan 25 | Feb 15 – Mar 1 | Feb 8 – Mar 15 | Oct 27 – Nov 24 |
| Kale | Jan 11 – Jan 25 | Feb 8 – Feb 22 | Feb 8 – Feb 22 | Oct 13 – Nov 3 |
| Broccoli | Jan 11 – Jan 25 | Feb 22 – Mar 8 | — | Sep 15 – Oct 6 |
| Cabbage | Jan 11 – Jan 25 | Feb 15 – Mar 1 | — | Sep 15 – Oct 6 |
| Cauliflower | Jan 11 – Jan 25 | Feb 22 – Mar 8 | — | Sep 15 – Oct 6 |
| Okra | Jan 25 – Feb 8 | Mar 29 – Apr 12 | Mar 29 – Apr 12 | — |
| Basil | Jan 25 – Feb 8 | Mar 15 – Mar 29 | — | — |
| Peas | — | — | Jan 25 – Feb 15 | Sep 29 – Oct 20 |
| Spinach | — | — | Jan 25 – Feb 15 | Oct 27 – Nov 17 |
| Radishes | — | — | Feb 1 – Mar 15 | Nov 10 – Dec 1 |
| Cucumbers | Feb 8 – Feb 15 | Mar 22 – Mar 29 | Mar 15 – Mar 29 | Oct 6 – Oct 20 |
| Zucchini & Summer Squash | Feb 8 – Feb 15 | — | Mar 15 – Mar 29 | Oct 13 – Oct 27 |
| Winter Squash & Pumpkins | Feb 8 – Feb 15 | — | Mar 15 – Mar 29 | — |
| Melons & Watermelon | Feb 8 – Feb 15 | Mar 22 – Apr 5 | — | — |
| Carrots | — | — | Feb 15 – Mar 15 | Sep 29 – Oct 13 |
| Beets | — | — | Feb 15 – Mar 15 | Oct 13 – Oct 27 |
| Potatoes | — | — | Feb 15 – Mar 8 | — |
| Swiss Chard | — | — | Feb 22 – Mar 22 | Oct 13 – Oct 27 |
| Cilantro | — | — | Feb 22 – Mar 15 | Oct 27 – Nov 17 |
| Green Beans | — | — | Mar 15 – Apr 5 | Oct 6 – Oct 20 |
| Sweet Corn | — | — | Mar 15 – Mar 29 | — |
| Sweet Potatoes | — | Mar 22 – Apr 12 | — | — |
| Garlic | — | — | — | Dec 8 – Jan 12 |
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 Mt Diablo Junction, CA weather station, 6 km away (elevation 2,169 ft (661 m)).
Frost dates near Diablo
- Danville Mar 8 · Dec 22
- Alamo Mar 8 · Dec 22
- Moraga Mar 8 · Dec 22
- San Ramon Feb 15 · Dec 2
- Clayton Mar 8 · Dec 22
- Walnut Creek Jan 7 · Dec 19
- Dublin Feb 15 · Dec 2
- Lafayette Jan 7 · Dec 19
- Concord Jan 9 · Dec 14
- Pleasant Hill Jan 7 · Dec 19
Frequently asked questions
When is the last frost in Diablo, CA?
The median last spring frost in Diablo, CA is March 8. There is still about a 10% chance of frost after April 15, so wait until then to plant frost-tender crops like tomatoes and peppers.
When is the first frost in Diablo, CA?
The median first fall frost is December 22, with about a 10% chance of frost before November 23.
How long is the growing season in Diablo, CA?
About 289 days between the median last spring frost and first fall frost.
What planting zone is Diablo, CA?
Diablo, CA is in USDA hardiness zone 9b.