Ticks in California

Ticks are active in California whenever the ground is not frozen, led by the Lyme-carrying deer tick. TickZone scores all 1091 California towns every morning, so risk stays local: pick your town for today's number, a 7-day outlook, and what's driving it.

Tick season in California

Tick season in California peaks in spring, the opposite of the Northeast. The Rocky Mountain wood tick, the main human biter across the interior West, quests from March into early summer and largely disappears as the high country dries out. On the Pacific slope the western blacklegged tick (the local Lyme vector) also peaks in spring, and in California's chaparral the Pacific Coast tick holds a late-summer window.

Generalized for the West, where risk peaks in spring and summer drought suppresses it.
Life stageJFMAMJJASOND
Rocky Mountain wood tick
Western blacklegged tick
Pacific Coast tick
American dog tick
Peak Active
Generalized for the West, where risk peaks in spring and summer drought suppresses it. Activity windows by life stage from TickEncounter (Univ. of Rhode Island) and the Northeast Regional Center for Excellence in Vector-Borne Diseases. Any warm spell can wake ticks earlier than the calendar suggests.

Summer heat is a low point out West, not a high one. The daily score on every town page folds the season, the weather, and local habitat into one number each morning, so it is the safer way to time hikes and yard work than the calendar alone.

Highest-risk towns in California (2026)

California's highest-risk towns are spread across several counties, led by Santa Cruz County (5 CDC-reported Lyme cases per 100k). The top 10 towns run 95 to 99 percent forest, ranked at peak season so the list stays stable.

  1. 1Lompico Santa Cruz CountyModerate at peak
  2. 2Brookdale Santa Cruz CountyModerate at peak
  3. 3Boulder Creek Santa Cruz CountyModerate at peak
  4. 4Mount Hermon Santa Cruz CountyModerate at peak
  5. 5Monte Rio Sonoma CountyModerate at peak
  6. 6Lexington Hills Santa Clara CountyModerate at peak
  7. 7Grizzly Flats El Dorado CountyModerate at peak
  8. 8Cedar Ridge Tuolumne CountyModerate at peak
  9. 9Tahoma El Dorado CountyModerate at peak
  10. 10Amador Pines Amador CountyModerate at peak

See the riskiest towns in every state →

All California towns, by county

Alameda County · 19 towns · 0/100k Lyme

Amador County · 11 towns

Butte County · 14 towns

Calaveras County · 8 towns

Colusa County · 4 towns

Contra Costa County · 49 towns

Del Norte County · 3 towns

El Dorado County · 13 towns

Fresno County · 29 towns

Glenn County · 3 towns

Humboldt County · 18 towns

Imperial County · 11 towns

Inyo County · 5 towns

Kern County · 52 towns

Kings County · 9 towns

Lake County · 14 towns

Lassen County · 3 towns

Los Angeles County · 141 towns · 0/100k Lyme

Madera County · 13 towns

Marin County · 23 towns

Mariposa County · 2 towns

Mendocino County · 9 towns · 6/100k Lyme

Merced County · 15 towns

Modoc County · 1 towns

Mono County · 1 towns

Monterey County · 23 towns

Napa County · 7 towns

Nevada County · 7 towns

Orange County · 42 towns

Placer County · 17 towns

Plumas County · 5 towns

Riverside County · 68 towns

Sacramento County · 30 towns

San Benito County · 3 towns

San Bernardino County · 47 towns

San Diego County · 51 towns · 0/100k Lyme

San Francisco County · 1 towns

San Joaquin County · 22 towns

San Luis Obispo County · 23 towns

San Mateo County · 30 towns

Santa Barbara County · 22 towns

Santa Clara County · 23 towns · 1/100k Lyme

Santa Cruz County · 26 towns · 5/100k Lyme

Shasta County · 12 towns

Sierra County · 1 towns

Siskiyou County · 10 towns

Solano County · 10 towns

Sonoma County · 23 towns · 2/100k Lyme

Stanislaus County · 25 towns

Sutter County · 3 towns

Tehama County · 7 towns

Trinity County · 4 towns

Tulare County · 26 towns

Tuolumne County · 11 towns

Ventura County · 24 towns

Yolo County · 10 towns

Yuba County · 8 towns

California tick questions

Are there ticks in California?
Yes. California has ticks, led by the Rocky Mountain wood tick across the interior and, on the Pacific slope, the western blacklegged tick. Lyme disease is uncommon here; the wood tick's spring bite (Rocky Mountain spotted fever, Colorado tick fever) is the real concern. Today 0 of the state's 1091 towns are at moderate or high tick risk on TickZone's daily score.
What types of ticks live in California?
California's human-biting ticks are the Rocky Mountain wood tick (Rocky Mountain spotted fever, Colorado tick fever, tularemia), the western blacklegged tick (the Pacific-slope Lyme vector), the Pacific Coast tick, and the American dog tick. See the California tick identification chart for photos and how to tell them apart.
When does tick season start and end in California?
In California, tick risk peaks in spring, the opposite of the Northeast. The Rocky Mountain wood tick quests from March into early summer, then summer heat and drought suppress activity. On the Pacific slope the western blacklegged tick also peaks in spring.
When is flea and tick season?
Flea and tick season in California centers on spring and early summer, when the Rocky Mountain wood tick and western blacklegged tick are most active, easing as the land dries in high summer. Start pet prevention by March.
Which tick carries Lyme disease in California?
On the Pacific slope, the western blacklegged tick (Ixodes pacificus) is the Lyme vector, but Lyme is uncommon across California. The Rocky Mountain wood tick, the main biter inland, does not carry Lyme; it carries Rocky Mountain spotted fever and Colorado tick fever.