What to do in Vallejo now
Vallejo is in warm-season grass country. Dates are typical for this spot, worked out from 23 years of weather at Napa County Airport; each status uses this year's soil estimates.
Cool-season: tall fescue, Kentucky bluegrass, perennial ryegrass, fine fescue
- Crabgrass pre-emergent Closed Mar 1 Typical: Feb 10 – Apr 22-inch soil held 55°F for a week from Mar 1, so crabgrass was sprouting. Next window: about Feb 10 – Apr 2, 2027.
- Seed or overseed Seed now · about 11 days left Typical: Aug 10 – Nov 144-inch soil is 55°, inside the 55–70°F range where tall fescue and bluegrass sprout fastest. The window typically closes around Nov 14.
- Late-fall feeding Soil rarely cools to 40°F Typical: Through winterRoots stay active through most winters here. Feed on the fall schedule your extension office gives for your grass, and avoid feeding a lawn that is dormant from drought.
Warm-season: bermudagrass, zoysia, St. Augustine, centipede, bahia
- Crabgrass pre-emergent Closed Mar 1 Typical: Feb 10 – Apr 22-inch soil held 55°F for a week from Mar 1, so crabgrass was sprouting. Next window: about Feb 10 – Apr 2, 2027.
- Seed or sod Wait for late spring Typical: Jun 2 – Aug 10Warm-season seed needs 4-inch soil at 65°F or more, and seedlings need the rest of summer to establish. Next window opens about Jun 2.
- Fall pre-emergent (Poa annua) Germinating since Aug 10 Typical: By Aug 104-inch soil fell below 70°F on Aug 10, when annual bluegrass begins to sprout. A pre-emergent now only stops later flushes; plan to apply by about Aug 10 next year.
- Dormancy and last feeding Expected about Nov 14 Typical: Around Nov 14Warm-season grass slows and browns once 4-inch soil stays under 55°F, typically Nov 14. Make the last nitrogen feeding at least a month before that.
The last 60 days and the week ahead
Vallejo soil is 4° cooler than normal for Nov 3, cooler than on 90% of those dates since 2005, and 6° cooler than a year ago.
The green line is our estimate of the daily average soil temperature 2 inches down, driven by temperatures at Napa County Airport, 11.3 km from the city center. The dashed part runs the National Weather Service forecast through the same model. Hover or tap for any day.
2-inch soil, estimated From the NWS forecast Normal Normal range (8 years in 10)
Show the numbers
| Date | 2-inch soil | 4-inch soil | Air high / low | Normal (2 in) |
|---|---|---|---|---|
| Oct 20 | 60° | 62° | 71° / 46° | 61° |
| Oct 21 | 60° | 62° | 68° / 50° | 61° |
| Oct 22 | 59° | 61° | 63° / 52° | 61° |
| Oct 23 | 60° | 62° | 75° / 48° | 60° |
| Oct 24 | 60° | 61° | 73° / 46° | 60° |
| Oct 25 | 60° | 61° | 75° / 43° | 60° |
| Oct 26 | 59° | 61° | 71° / 45° | 60° |
| Oct 27 | 57° | 59° | 67° / 38° | 59° |
| Oct 28 | 56° | 58° | 71° / 38° | 59° |
| Oct 29 | 56° | 58° | 70° / 42° | 58° |
| Oct 30 | 56° | 58° | 67° / 47° | 58° |
| Oct 31 | 55° | 57° | 63° / 40° | 58° |
| Nov 1 | 54° | 56° | 67° / 40° | 57° |
| Nov 2 | 54° | 56° | 67° / 41° | 57° |
| Nov 3 | 53° | 55° | 58° / 43° | 57° |
| Nov 4 (forecast) | 54° | 56° | 62° / 52° | 56° |
| Nov 5 (forecast) | 55° | 56° | 64° / 52° | 56° |
| Nov 6 (forecast) | 56° | 57° | 64° / 53° | 56° |
| Nov 7 (forecast) | 57° | 58° | 69° / 50° | 55° |
| Nov 8 (forecast) | 58° | 59° | 69° / 51° | 55° |
| Nov 9 (forecast) | 58° | 59° | 68° / 50° | 55° |
Which grass grows in Vallejo
With mild winters (January averages 48°F), most Vallejo lawns are warm-season grasses such as bermudagrass, St. Augustine, zoysia and centipede. They grow through summer and slow or go dormant in winter.
Vallejo soil through the year
Weekly 2-inch estimates for 2026 so far against 2025 and the normal for each week. The red lines mark 50°F, when crabgrass pre-emergent should be down, and 65°F, when warm-season seed sprouts well.
2026 2025 Normal (2005–2025) 8 years in 10
Normal by month
| Month | 2 in | 4 in | Air |
|---|---|---|---|
| Jan | 47° | 48° | 48° |
| Feb | 49° | 50° | 51° |
| Mar | 52° | 53° | 53° |
| Apr | 55° | 57° | 56° |
| May | 61° | 62° | 60° |
| Jun | 66° | 67° | 65° |
| Jul | 68° | 70° | 67° |
| Aug | 68° | 70° | 67° |
| Sep | 67° | 68° | 66° |
| Oct | 62° | 63° | 61° |
| Nov | 53° | 55° | 53° |
| Dec | 47° | 48° | 47° |
Soil: average of our daily estimates, 2005–2025. Air: NOAA 1991–2020 normals for the station.
Typical lawn dates in Vallejo
Each date is when the soil estimate (or the air, for freezes) crossed the threshold, year by year since 2005. “Early” and “late” are the 10th and 90th percentile years, so 8 years in 10 fall between them.
| Event | Typical | 2026 |
|---|---|---|
| Last spring freeze (32°F) | Mar 25 | Feb 20 |
| Crabgrass model: 250 growing degree days | Jan 17 | Jan 14 |
| Pre-emergent window opens (2-inch soil 50°F) | Feb 10 | Feb 5 |
| Crabgrass begins to sprout (2-inch soil 55°F) | Apr 2 | Mar 1 |
| Cool-season lawns start growing (4-inch soil 55°F) | Mar 31 | Mar 1 |
| Warm-season seeding opens (4-inch soil 65°F) | Jun 2 | May 21 |
| Cool-season seeding opens (4-inch soil under 70°F) | Aug 10 | Aug 10 |
| Cool-season seeding ends (4-inch soil under 55°F) | Nov 14 | not yet |
| Warm-season grass goes dormant (4-inch under 55°F) | Nov 14 | not yet |
| First fall freeze (32°F) | Nov 15 | not yet |
Where these numbers come from
There is no soil sensor in most cities, so we estimate it. Shallow soil follows air temperature with a lag of a few days, and runs a little warmer than the air in fall. We fitted that relationship to 190 USDA soil-sensor stations; on years held out of the fit, the estimate was off by 3.3°F on an average day, and it put the spring 55°F date within a median of 3 days. Read the methodology.
Weather: RCC ACIS station KAPC (NAPA COUNTY AIRPORT), daily data since 1998. Forecast: National Weather Service, STO office, issued Nov 4, 2026, 4:00 AM EST. Last observed day: Nov 3, 2026.
Vallejo questions
What is the soil temperature in Vallejo today? Our estimate for Nov 3 is 53°F at 2 inches and 55°F at 4 inches, as a daily average. Early-morning soil runs a few degrees cooler than that, and afternoon soil warmer.
When should I put down crabgrass pre-emergent in Vallejo? Apply when 2-inch soil holds about 50°F and before it holds 55°F. That has typically been Feb 10 to Apr 2 in Vallejo. For 2026 the window closed on Mar 1.
When can I seed bermudagrass in Vallejo? Wait for late spring. Warm-season seed needs 4-inch soil at 65°F or more, and seedlings need the rest of summer to establish. Next window opens about Jun 2.
Is it too late to fertilize in Vallejo? Expected about Nov 14. Warm-season grass slows and browns once 4-inch soil stays under 55°F, typically Nov 14. Make the last nitrogen feeding at least a month before that.
When is the last frost in Vallejo? The last 32°F night of spring has typically come around Mar 25, and as late as May 1 in 1 year in 10. The first fall freeze typically arrives around Nov 15.
Why 2 inches and 4 inches? Crabgrass and most weed seeds sprout in the top inch or two, so pre-emergent timing follows 2-inch soil. Grass seed and roots respond to the slightly steadier soil at about 4 inches.
How accurate is this? It is a model, not a probe in your yard. Expect about 3–4°F of difference on a given day; shade, slope, mulch and irrigation all move real soil. The dates and trends are more reliable than any single day.