Frost dates for Santa Rosa, California
In Santa Rosa, half of springs have had their last frost by March 2 (and 1 spring in 10 still has one after April 2), and half of falls have had their first frost by November 20, leaving about 262 frost-free days in a typical year. Here is how sure those dates are, what they mean for planting, and where they come from.
Frost dates for
Santa Rosa, California
Last spring frost
March 2
Half of springs have their last frost by this date. For a safer bet, wait until April 2: only 1 spring in 10 has a frost after that.
First fall frost
November 20
Half of falls have their first frost by this date. In 1 fall in 10 it comes by November 1.
Growing season
262 days
Frost-free days in a typical year. 9 years in 10 get at least 223.
Hardiness zone
9b
2023 USDA map: the coldest night of winter averages 25°F to 30°F. It was 9b on the 2012 map too. ZIP codes within about 6 miles of the city's center: 5 in 9a and 2 in 9b.
Stations near you disagree. NOAA's Santa Rosa Sonoma Co Airport (7 miles away, at 110 feet above sea level), the one we used, gives a typical last frost of March 2 and a typical first frost of November 20. NOAA's Graton (9 miles away, at 200 feet above sea level) gives a typical last frost of March 20 and a typical first frost of November 13. So the typical last frost could fall anywhere from March 2 to 20 and the typical first frost from November 13 to 20, depending on whether your garden is more like one or the other. Local terrain matters: hillsides, valley floors, water and city heat can change frost dates a lot over a few miles. Treat the dates here as a starting point, and compare with a nearby gardener or your county extension office.
Print a year planner for Santa Rosa
Frost risk through the year
How sure are these dates?
A frost date is a probability, not a promise. NOAA worked out, from 30 years of nightly lows, how often the last spring frost and the first fall frost fall on each date. The middle column is the typical year. The outer columns are the early and late years that come about once a decade.
| Early year 1 in 10 | Typical year 1 in 2 | Late year 1 in 10 | |
|---|---|---|---|
| Last frost in spring | January 27 | March 2 | April 2 |
| First frost in fall | November 1 | November 20 | December 10 |
The frost-free season between them runs 262 days in a typical year. In 1 year in 10 it is 307 days or longer, and in 1 year in 10 it is 223 days or shorter.
- Hard freeze (28°F): about 91 years in 100 have one. In those years the last typically comes on January 23 and the first on December 5. It is a harder freeze than the 32°F frost line, cold enough to damage many garden plants; how hardy a crop is decides whether it comes through. (The National Weather Service's own hard-freeze threshold varies from office to office.)
- Frost possible (36°F at the station): typically last on April 12 and first on November 3. On clear, still nights the ground can be several degrees colder than the thermometer, so frost can form on plants when the official reading is in the mid-30s.
In 8 springs out of 10, the last frost in Santa Rosa comes between January 27 and April 2, a window of 65 days. That is wider than at most NOAA stations (the typical window is 31 days), so spring here is less predictable than average: lean toward the later date.
Among California's 169 NOAA stations with a frost every year, 78 percent have their typical last frost later than Santa Rosa does.
Planting calendar for Santa Rosa
These dates count from the typical last and first frosts, using the planting rules published by Colorado State University Extension (spring), Virginia Cooperative Extension (fall crops) and University of Minnesota Extension (garlic, where winters are hard). Weather in any one year can run early or late, so check the forecast before you plant tender crops.
We don't give a garlic date here. The rule we use, from the University of Minnesota Extension, counts from the first killing frost, and it works where a hard freeze comes every year before the ground freezes. Your county's extension office can tell you when to plant garlic in your climate.
| When | What to do | Why then |
|---|---|---|
| January | ||
| January 12 to February 2 | Eggplant Start seeds indoors | 6 to 9 weeks before planting out |
| January 19 to February 2 | Peppers Start seeds indoors | 6 to 8 weeks before planting out |
| January 26 to February 9 | Tomatoes Start seeds indoors | 5 to 7 weeks before planting out |
| February | ||
| February 2 to 16 | Peas, spinach, lettuce, radishes, onion sets, turnips Sow outdoors, as early as | hardy crops: 2 to 4 weeks before the typical last frost |
| February 2 to 16 | Broccoli and cabbage Plant out, as early as | hardy crops: 2 to 4 weeks before the typical last frost |
| February 16 to March 2 | Beets, carrots, potatoes, Swiss chard Plant outdoors, as early as | semi-hardy crops: up to 2 weeks before the typical last frost |
| February 16 to March 2 | Cauliflower Plant out, as early as | semi-hardy: up to 2 weeks before the typical last frost |
| March | ||
| March 2 | Snap beans, sweet corn, cucumbers, summer squash Sow outdoors around | tender crops: around the typical last frost date |
| March 16 | Tomatoes, peppers, eggplant Plant out from | very tender: 2 weeks or more after the typical last frost |
| March 16 | Melons, winter squash, pumpkins, lima beans Sow outdoors from | very tender: 2 weeks or more after the typical last frost |
| June | ||
| June 25 to July 9 | Cabbage for fall Start seeds | set the plants out by August 13 |
| July | ||
| July 15 to 29 | Broccoli for fall Start seeds | set the plants out by September 2 |
| August | ||
| August 24 | Snap beans for fall Last date to sow | 60 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| August 28 | Carrots for fall Last date to sow | 70 days to harvest, plus 2 weeks for slower fall growth |
| August 29 | Cucumbers for fall Last date to sow | 55 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| September | ||
| September 2 | Peas for fall Last date to sow | 65 days to harvest, plus 2 weeks for slower fall growth |
| September 3 | Summer squash for fall Last date to sow | 50 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| September 7 | Leaf lettuce and beets for fall Last date to sow | 60 days to harvest, plus 2 weeks for slower fall growth |
| September 17 | Turnips and kohlrabi for fall Last date to sow | 50 days to harvest, plus 2 weeks for slower fall growth |
| September 27 | Spinach for fall Last date to sow | 40 days to harvest, plus 2 weeks for slower fall growth |
| October | ||
| October 7 | Radishes for fall Last date to sow | 30 days to harvest, plus 2 weeks for slower fall growth |
| November | ||
| November 1 | Tomatoes, peppers, squash, melons, cucumbers Watch the forecast from | in 1 fall in 10 the first frost comes by this date; pick tender crops before a frost |
| December | ||
| December 15 to January 12 | Broccoli and cabbage Start seeds indoors | 5 to 7 weeks before planting them out |
| December 29 to January 26 | Cauliflower Start seeds indoors | 5 to 7 weeks before planting out |
Want more insurance? Shift every spring date 31 days later. That plans around April 2, the date after which only 1 spring in 10 has a frost.
For spring bulbs such as tulips and daffodils, plant once the soil has cooled to about 50 to 55°F and keep going until a couple of weeks before the ground freezes. Our guide to fall planting explains how to tell.
Where these numbers come from
These dates come from NOAA's weather station Santa Rosa Sonoma Co Airport (station USW00023213), 7 miles from the center of Santa Rosa. It sits at about the same elevation, 110 feet above sea level. NOAA rates this station's record as representative: at least 10 of the 30 years, with the gaps filled from nearby stations.
The same station also gives the frost dates for Rohnert Park and Windsor.
Our ZIP code lookup matches these 3 ZIP codes to the same station, so they get the same dates: 95401, 95439, 95492. Hardiness zones are worked out separately for each ZIP code.
Nearby places
- Vallejo, California: last frost around March 5, first frost around November 21 (35 miles away)
- Fairfield, California: frost not every year (40 miles away)
- Richmond, California: frost not every year (40 miles away)
See frost dates across California, or look up your own ZIP code for the station nearest you. Want the background? Read what a last frost date really means.