Los Angeles
Apply ASAP67°F↓ cooling
Soil has cooled to 75°F, so winter weeds are sprouting. Pre-emergent still stops later flushes.
Winter weeds are sprouting now
California Weed Watch · updated Nov 3, 1:18 AM CT
When to apply pre-emergent in California
Live soil temperatures for Los Angeles, San Diego, San Jose, Sacramento and Fresno, updated every three hours. Weeds sprout by soil temperature, not by the calendar, so the right week moves from year to year.
California lawns get pre-emergent twice a year: in spring for crabgrass and other summer weeds, and in fall for winter weeds.
Spring pre-emergentNext season
Typically Jan 24 – Mar 26
Stops crabgrass and other summer weeds before they sprout.
Fall pre-emergentThis season
Typically by Aug 20 – Sep 23
Stops winter weeds (annual bluegrass, henbit, chickweed) before they sprout.
Skip it if you are overseeding this fall.
Right now · fall pre-emergent season
Winter weeds are germinating — apply now if you haven't: Los Angeles, San Diego, Sacramento and Fresno. Winter weeds are up — spot-treat: San Jose
Soil is 57–68°F now. They keep coming up in flushes into winter, so pre-emergent still helps. Overseeding this fall? Skip pre-emergent — it stops grass seed too.
Soil temperature by city
Soil 2 inches down, 5-day average: solid line = the last two weeks, dashed = the six-day forecast. Shaded = below 75°F, where winter weeds sprout — pre-emergent has to be down before the line gets there.
San Diego
Apply ASAP68°F→ steady
Soil has cooled to 75°F, so winter weeds are sprouting. Pre-emergent still stops later flushes.
Winter weeds are sprouting now
San Jose
Spot-treat60°F→ steady
Winter weeds are up. Spot-treat them on a mild day, or in early spring before they flower.
Winter weeds are up
Sacramento
Apply ASAP57°F→ steady
Soil has cooled to 75°F, so winter weeds are sprouting. Pre-emergent still stops later flushes.
Winter weeds are sprouting now
Fresno
Apply ASAP61°F↓ cooling
Soil has cooled to 75°F, so winter weeds are sprouting. Pre-emergent still stops later flushes.
Winter weeds are sprouting now
California pre-emergent calendar
Spring pre-emergent stops crabgrass. The window runs from the typical day soil warms to 50°F to the day it holds 55°F, when crabgrass starts germinating (2016–2025). Fall pre-emergent stops winter weeds: have it down a week before soil usually cools to 75°F, when they start germinating.
| City | Spring pre-emergent (crabgrass) | Fall pre-emergent (winter weeds) |
|---|---|---|
| Los Angeles | Jan 29 – Feb 8 | Apply by Sep 23 |
| San Diego | Jan 26 – Feb 9 | Apply by Sep 7 |
| San Jose | Jan 24 – Feb 15 | Apply by Aug 20 |
| Sacramento | Feb 22 – Mar 26 | Apply by Sep 3 |
| Fresno | Feb 6 – Feb 23 | Apply by Sep 13 |
These are typical-year dates (the median of 2016–2025); any one year can run a couple of weeks earlier or later, which is what the live readings above are for. For your exact yard, check soil temperature by ZIP.
Recommended gear
Fall pre-emergents
Granular or liquid. Follow the label rate, and water it in.
Paid links. As an Amazon Associate, MeasureLawn earns from qualifying purchases.
Amazon
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Scotts Halts Crabgrass & Grassy Weed Preventer
Beginner friendlyPendimethalingranularcovers ~5,000 sq ft / 0.11 ac$24.97as of Nov 2, 10:00 AM UTC · may change
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The Andersons Barricade Professional-Grade Granular
Beginner friendly0.48% Prodiaminegranularcovers ~12,880 sq ft / 0.30 ac$79.88as of Nov 2, 10:00 AM UTC · may change
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Dimension 2EW (Dithiopyr)
Liquid concentrate; 64 oz half gallon; mix with water and spray
Dithiopyrliquidcovers ~91,428 sq ft / 2.1 ac$158.00as of Nov 2, 10:00 AM UTC · may change
What people in California are identifying
We record the state each identification comes from. California's list appears here once it has at least 40 identifications spread over 7 or more days — so no single scan stands out. Until then, see the national list, or add yours:
Identify a weed from a photoWeeds to watch in California this fall
Questions about California
When should I apply crabgrass pre-emergent in California?
Put crabgrass pre-emergent down as soil warms to 50°F, before it holds 55°F and crabgrass starts germinating. In a typical year (2016–2025) that window is Jan 29 – Feb 8 in Los Angeles; Jan 26 – Feb 9 in San Diego; Jan 24 – Feb 15 in San Jose; Feb 22 – Mar 26 in Sacramento; Feb 6 – Feb 23 in Fresno.
When should I apply fall pre-emergent in California?
Winter weeds such as annual bluegrass, henbit and chickweed start germinating as soil cools to about 75°F in late summer and fall, and most come up once it is below 70°F. Have fall pre-emergent down before they start: typically by Sep 23 in Los Angeles; by Sep 7 in San Diego; by Aug 20 in San Jose; by Sep 3 in Sacramento; by Sep 13 in Fresno. Skip it if you are overseeding this fall, because it stops grass seed too.
What is the soil temperature in California right now?
As of Nov 3, 1:18 AM CT: Los Angeles 67°F, San Diego 68°F, San Jose 60°F, Sacramento 57°F, Fresno 61°F (5-day average, about 2.4 inches down). Winter weeds are germinating — apply now if you haven't: Los Angeles, San Diego, Sacramento and Fresno. Winter weeds are up — spot-treat: San Jose.
How the readings and dates are made, and their limits: Weed Watch method. Soil data: Open-Meteo.com (CC BY 4.0); typical dates: NASA POWER.