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When Is Tick Season?

Ticks are most active from April through September, but exposure can happen year round. Nymphs quest from April through July and pose a particularly high risk. Adults are most active in early spring and fall, and blacklegged tick adults may search for a host any time winter temperatures rise above freezing.

Most people picture tick season as one block on the calendar, roughly summer. A tick's biting season depends on which life stage is out hunting, and the stages take turns across the year. Get the stages straight and the calendar makes sense, including why the riskiest ticks arrive early.

What months is tick season?

The CDC puts it plainly on its Preventing Tick Bites page: "Tick exposure can occur year-round, but ticks are most active during warmer months (April-September)." NIOSH, the CDC's occupational safety arm, frames the same window for outdoor workers: "Ticks may be active all year in some regions with warmer weather. In the United States, they are most active in the spring, summer, and fall."

April to September is the core, spring through fall is the broader risk window, and the shoulders never fully close. The tighter answer depends on the tick.

Why do nymphs in late spring and summer matter most?

Most ticks go through four life stages. The CDC describes them as "egg, six-legged larva, eight-legged nymph, and adult," and notes that after hatching, "ticks must eat blood at every stage to survive." The infection math follows from that feeding schedule. As the CDC puts it, "Ticks usually acquire pathogens early in their life (larval or nymphal stages) when they feed on animals. They transmit those pathogens to other animals or to people later in their life (nymphal or adult stages)."

For the blacklegged tick, the species behind Lyme disease in the eastern United States, the CDC gives the timing directly: "From April through July, nymphs are actively questing for hosts in the environment, and in early spring and fall seasons, adults are most active."

That April to July nymph window is the part worth circling. The CDC explains why: "Nymphal ticks pose a particularly high risk due to their abundance and small size (about the size of a poppy seed), which makes them difficult to see. Lyme disease patients are often not even aware of a tick bite before getting sick." Adult females can transmit the same bacteria, but per the CDC they "are more likely to be noticed and removed before transmission due to their larger size (about the size of sesame seed)."

The case data lines up with the nymph calendar. The CDC logged 275,589 reported Lyme disease cases from 2008 through 2015, and date of illness onset was available for 200,108 of them. Among those, "for all years, the first week in July was the peak week of illness onset for confirmed and probable cases."

When are adult ticks active, and does fall count?

Fall counts. The CDC's own surveillance authors made the point explicitly in that same report: the seasonal pattern "underscores that adult ticks that seek blood meal hosts during the fall months have a proportional role in human illness and that prevention messages should not be focused only during the spring and summer season when nymphal ticks seek hosts."

That is a public health agency telling its own field not to shut off the message on Labor Day. The CDC's blacklegged tick page agrees: "the greatest risk of being bitten exists in the spring, summer, and fall," with nymphs and adult females the stages most likely to bite humans.

Can you get a tick bite in winter?

Yes, and the threshold is lower than most people expect. The CDC states that blacklegged tick adults "may be out searching for a host any time winter temperatures are above freezing." Its Lyme prevention page adds that "most cases of Lyme disease are reported in the summer months, though Lyme disease cases occur year-round."

Field research gives a number. Duffy and Campbell, publishing in the Journal of Medical Entomology in 1994, ran winter flagging experiments on Long Island and reported that adult Ixodes scapularis "have an apparent threshold of questing activity at 4 degrees C," roughly 39 degrees Fahrenheit. Their conclusion was aimed squarely at public messaging: "This threshold should be incorporated into public education efforts because the public may be at risk of contracting Lyme disease any time during the winter when temperatures exceed 4 degrees C."

A 40-degree January afternoon is not tick-free.

Winter cases also look different clinically. In the CDC surveillance data, among patients with illness onset during the coldest months, December through March, arthritis was the most common clinical sign. Erythema migrans, the expanding rash, was the most common sign for onsets from April through November.

Does tick season change depending on where you live?

Substantially. Start with which ticks are even present. The CDC maps the blacklegged tick as "widely distributed across the eastern United States" and the western blacklegged tick "along the Pacific coast of the United States, particularly northern California." The American dog tick is "widely distributed east of the Rocky Mountains," the Gulf Coast tick sits "primarily in the southeastern United States," and the Rocky Mountain wood tick occupies "Rocky Mountain states and southwestern Canada from elevations of 4,000 to 10,500 feet."

Then the calendars diverge. On the Pacific coast the pattern nearly inverts the eastern one. The California Department of Public Health reports that for the western blacklegged tick, "nymphs are most active in spring and early summer, and adult ticks are most active from fall through early spring." CDPH also notes that "risk of exposure varies throughout California," and that in some parts of the state a higher share of nymphs carry Lyme disease bacteria, an average of 5 to 15 percent, than adults, an average of 1 to 2 percent.

Disease burden is regional too. The CDC's surveillance summary found that fourteen states in the Northeast, mid-Atlantic, and upper Midwest accounted for 95.2 percent of all reported Lyme disease cases during 2008 through 2015, and current CDC guidance still places most cases in those regions, with some on the Pacific Coast.

Do other tick species follow the same calendar?

No, and the lone star tick is the clearest example. Writing in the CDC journal Emerging Infectious Diseases in 2019, Telford and colleagues summarized its phenology: "Across their wide distribution south of New York, adult lone star ticks seek hosts mid-March through late June; nymphs, mid-May through late July; and larvae, July through September." Larvae, they wrote, "seem to feed mainly during late summer and early fall," with modeling suggesting a temperature threshold near 17 degrees Celsius, about 63 degrees Fahrenheit, for larval host seeking.

That paper exists because the calendar moved. Dragging on June 7, 2018 on Long Island, New York and June 18, 2018 on Naushon Island, Massachusetts, the authors found larval clusters "reminiscent of those of lone star ticks typically encountered during August or September."

The CDC calls the lone star tick "a very aggressive tick that bites humans," widely distributed in the Northeast, South, and Midwest, with nymphs and adult females the stages that most frequently bite people. For the American dog tick, the CDC says "the highest risk of being bitten occurs during spring and summer," and adult females are the ones most likely to bite humans.

What does the CDC recommend during tick season?

The CDC's stated principle is that "reducing exposure to ticks is the best defense against tickborne diseases." Its recommendations include:

  • Use EPA-registered insect repellents containing DEET, picaridin, IR3535, oil of lemon eucalyptus, para-menthane-diol, or 2-undecanone, and look for an EPA registration number on the label.
  • Treat clothing and gear with products containing 0.5 percent permethrin, which the CDC says remains protective through several washings.
  • Avoid wooded and brushy areas with high grass and leaf litter, and walk in the center of trails.
  • Check your body for ticks after being outdoors, including under the arms, in and around the ears, inside the belly button, behind the knees, in and around the hair, between the legs, and around the waist.
  • Tumble dry clothes on high heat for 10 minutes to kill ticks on dry clothing after coming indoors.
  • Shower soon after being outdoors. The CDC says showering within two hours of coming indoors has been shown to reduce the risk of getting Lyme disease.
  • Remove attached ticks as soon as possible, and do not wait to see a healthcare provider to remove one. The CDC states that removing attached ticks within 24 hours can help prevent Lyme disease.

This is not only a wilderness problem. The CDC notes that "many people get ticks in their own yard or neighborhood," and that many people who develop Lyme disease are exposed in their own yards rather than in wooded or rural areas.

Where Longsleeve fits

Longsleeve is an EPA-registered picaridin lotion (EPA Reg. No. 101457-1). It repels mosquitoes and ticks for up to 14 hours. It is fragrance-free, with nine disclosed ingredients.

Common questions

When does tick season start?

The CDC says ticks are most active during warmer months, April through September, but that tick exposure can occur year-round. For blacklegged ticks, nymphs are actively questing from April through July, and adults are most active in early spring and fall.

Is there a temperature below which ticks stop biting?

The CDC says blacklegged tick adults may search for a host any time winter temperatures are above freezing. Research published in the Journal of Medical Entomology in 1994 found an apparent questing threshold of 4 degrees Celsius, about 39 degrees Fahrenheit, for adult Ixodes scapularis on Long Island.

Which life stage is riskiest?

The CDC says nymphal ticks pose a particularly high risk because of their abundance and their small size, about that of a poppy seed, which makes them hard to see. The California Department of Public Health likewise reports that nymphs pose a higher risk of disease transmission than adult ticks.

Should I stop worrying about ticks after summer?

No. CDC surveillance authors concluded that adult ticks seeking hosts in fall have a proportional role in human illness, and that prevention messages should not focus only on the spring and summer nymph season. The CDC lists fall alongside spring and summer as the period of greatest bite risk for blacklegged ticks.

What if I find a tick or feel sick after a bite?

Remove the tick as soon as possible rather than waiting for an appointment. The CDC says to see your doctor if you develop a rash or fever within several days to weeks after removing a tick, and to tell them when the bite happened and where you likely acquired the tick. Any medical decision belongs with your clinician.

Sources

  1. CDC, Preventing Tick Bites. https://www.cdc.gov/ticks/prevention/index.html
  2. CDC, Where Ticks Live. https://www.cdc.gov/ticks/about/where-ticks-live.html
  3. CDC, How Lyme Disease Spreads. https://www.cdc.gov/lyme/causes/index.html
  4. CDC, Tick Lifecycles. https://www.cdc.gov/ticks/about/tick-lifecycles.html
  5. CDC, Preventing Lyme Disease. https://www.cdc.gov/lyme/prevention/index.html
  6. CDC, What to Do After a Tick Bite. https://www.cdc.gov/ticks/after-a-tick-bite/index.html
  7. CDC NIOSH, Tickborne Diseases in Workers. https://www.cdc.gov/niosh/outdoor-workers/about/tick-borne-diseases.html
  8. Schwartz AM, Hinckley AF, Mead PS, Hook SA, Kugeler KJ. Surveillance for Lyme Disease, United States, 2008 to 2015. MMWR Surveillance Summaries, November 10, 2017;66(22):1-12. https://www.cdc.gov/mmwr/volumes/66/ss/ss6622a1.htm
  9. CDC Newsroom, CDC Data Show Weekly ER Visits for Tick Bites Higher than Usual, 2026. https://www.cdc.gov/media/releases/2026/2026-cdc-data-show-weekly-er-visits-for-tick-bites-higher-than-usual.html
  10. Telford SR III, Buchthal J, Elias P. Early Questing by Lone Star Tick Larvae, New York and Massachusetts, USA, 2018. Emerging Infectious Diseases, Volume 25, Number 8, August 2019. https://wwwnc.cdc.gov/eid/article/25/8/18-1293_article
  11. Duffy DC, Campbell SR. Ambient air temperature as a predictor of activity of adult Ixodes scapularis (Acari: Ixodidae). Journal of Medical Entomology, 1994;31(1):178-80. https://pubmed.ncbi.nlm.nih.gov/8158624/
  12. California Department of Public Health, Lyme Disease and Other Tick-Borne Diseases in California. https://www.cdph.ca.gov/Programs/CID/DCDC/CDPH%20Document%20Library/2017LymeDiseaseinCABrochure.pdf
  13. California Department of Public Health, Seasonal Risk of Exposure to Infected Western Blacklegged (Ixodes pacificus) Ticks in California. https://www.cdph.ca.gov/Programs/CID/DCDC/CDPH%20Document%20Library/SeasonalTickRiskGraphic.pdf
  14. CDC, Signs and Symptoms of Lyme Disease. https://www.cdc.gov/lyme/signs-symptoms/index.html

Last reviewed 2026-08-05 · every claim on this page is sourced above