Mosquito and Tick Season by Region: When Bug Season Starts
There is no single start date. For blacklegged ticks, CDC says nymphs are most active from April through July and adults in early spring and fall. West Nile mosquito season typically runs June through October, peaking in late August and early September. Local weather and species shift all of this, so confirm with your health department.
Lemon Eucalyptus Essential Oil
Our own Lemon Eucalyptus Essential Oil, in sizes from 0.5 oz to bulk.
From $9.99
Shop Now →Last reviewed: October 2026. We sell lemon eucalyptus essential oil, which is not a registered insect repellent, and nothing below is a claim about it. This page is a calendar built only from CDC statements we could open and read.
Read this first: what this calendar is and is not
Most "bug season by state" charts online give exact months per state with no source. CDC does not publish that table for ticks or mosquitoes, and we are not going to invent one. What CDC does publish is activity by species and life stage, plus broad regional ranges. Our method was simple: open each CDC page, copy the timing statements it makes, and sort them by region. Where CDC is silent, the table says so. For your county, CDC itself points readers to the "local health department or Cooperative Extension office."
That is a real limit. A warm spring, a mild winter or a wet summer moves everything. Treat the windows below as the earliest sensible time to start protecting yourself, not as a promise that bugs are absent outside them.
Step 1: know which bug you are planning for
Ticks and mosquitoes follow different clocks. Mosquitoes track warm weather and standing water. Ticks track a life cycle that takes years. CDC says the blacklegged tick (Ixodes scapularis) life cycle "generally lasts two years," with eggs laid in spring, larvae hatching in summer, nymphs feeding the following spring and molting into adults in fall. The western blacklegged tick (Ixodes pacificus) cycle generally lasts three years.
The practical result is that the tick risk you worry about in June (small nymphs) is a different animal from the one in October (adults). Nymphs are immature ticks, smaller than adults and so easier to miss on a skin check, which is our reasoning, not a CDC statement. CDC says adults are most active in early spring and fall.
Step 2: the calendar, by region
| Region (per CDC) | Tick timing CDC states | Mosquito timing CDC states | Gaps |
|---|---|---|---|
| Northeast, mid-Atlantic, north-central states (forested areas) | Infected blacklegged ticks may bite "from spring through the fall." Nymphs actively quest April through July; adults are most active early spring and fall. | West Nile mosquito season is summer into fall, typically June through October; CDC says human cases usually peak in late August and early September. | No state-by-state start dates from CDC. |
| Southeast | CDC says blacklegged ticks in most of the southeastern U.S. are almost never infected with the Lyme bacterium. It lists the lone star tick as widely distributed in the Northeast, South and Midwest and the Gulf Coast tick as primarily southeastern. | A CDC official said in a 2012 briefing that West Nile cases occur a little later in the north than in the south, by a couple of weeks. | The pages we opened give no month ranges for lone star or Gulf Coast ticks. |
| Midwest | Blacklegged ticks are widely distributed in the east; lone star and American dog ticks also occur (American dog tick east of the Rockies). | As above: June through October for West Nile in most regions. | No Midwest-specific month ranges. |
| Pacific Coast, especially northern California | Western blacklegged ticks live along the coast. CDC says adult females seek a winter or spring blood meal before laying eggs in spring. | West Nile cases have been reported in every state in the contiguous U.S. (CDC), and the national June through October figure is the only season CDC gives. | No month-by-month CDC table for the Pacific states. |
| Anywhere in the lower 48 | CDC tick pages say the greatest risk is spring, summer and fall. | CDC says infection happens during mosquito season; the national window is typically June through October. | Warm spells can start activity earlier. Local data wins. |
The same statements read differently depending on where you live. In Connecticut or Wisconsin, "spring through fall" for infected ticks is a real, long window. In Georgia, most blacklegged ticks are not carrying the Lyme bacterium, but other ticks and other tickborne illnesses still apply, which is a good moment to ask your local extension office what is circulating.
Step 3: the dates that matter on a calendar
- March to May: Start tick checks and gear prep. CDC says adult blacklegged ticks are most active in early spring, and nymphs are questing by April.
- Late spring to early summer: Nymph season. Pay attention to leaf litter, tall grass and trail edges. CDC advises walking in the center of trails.
- June: Start of the typical West Nile mosquito window nationwide.
- Late August to early September: Peak West Nile cases, per CDC.
- October to November: Adult blacklegged ticks again. Our companion piece on tick protection for hunting and fall tick season covers the fall side.
- Winter: CDC's life-cycle page notes adult western blacklegged females seeking winter blood meals. We found no CDC statement that all ticks are inactive in winter, so do not assume a freeze means the season is over everywhere.
Mosquitoes: why the calendar is looser
Ticks follow a multi-year cycle, so their timing is fairly predictable. Mosquitoes do not. CDC describes Aedes mosquitoes as living "in many areas of the United States" and needing only a small amount of water in a container to lay eggs, and its dengue page says they bite during the day and night. The practical result is that a warm, wet spell can produce biting mosquitoes in a yard well before the national West Nile window opens, and a dry spell can leave a yard quiet in July. The national figure is a floor for planning, not a forecast for your block.
It also means the question "when does mosquito season start" has a different answer in a city with storm drains and planters than in a dry hillside. If you want to cut your own yard's mosquitoes, the lever is water, and we cover it in our backyard guide.
What to do with the dates
We would build a plan around two prompts, not a start date.
- Start earlier than you think. If you spend time in grass, brush or woods, begin the checks CDC describes when spring starts, not when you first see a tick.
- Keep going later than you think. CDC's fall adult activity and September West Nile peak fall after most people have put away their bug routine.
The CDC habits themselves are the same all year: use an EPA-registered repellent with one of the listed active ingredients and check the label for an EPA registration number; apply sunscreen first and repellent second; wear pretreated clothing or treat gear with 0.5 percent permethrin; shower within two hours of coming indoors; do a full-body check; tumble clothes on high for 10 minutes. We list them with sources in how to prevent tick bites and in does lemon eucalyptus repel ticks.
A word on repellents and our oil
Registered repellents containing oil of lemon eucalyptus (OLE) or PMD appear on CDC's list of active ingredients. CDC says not to use OLE or PMD products on children under 3. Our own bottle is the essential oil, not the registered product, and we do not claim it repels ticks or mosquitoes. If you want to understand the difference, see our guide to oil of lemon eucalyptus. If you simply like the scent for the porch, our shop carries it, but not as bite protection.
Frequently asked questions
When does tick season start?
For blacklegged ticks, CDC says adults are active in early spring and nymphs are actively questing from April through July. Your local timing depends on temperature, so start precautions at the first warm spells.
When does mosquito season end?
CDC describes West Nile virus season as summer into fall, typically June through October. In 2012 a CDC official said he expected transmission to continue until October in most regions of the country.
Is the South safer from Lyme disease?
Per CDC, blacklegged ticks in most of the southeastern U.S. are almost never infected with the Lyme bacterium. That does not make the region free of ticks; other species live there and carry other pathogens. Ask your local health department what applies.
How long must a tick be attached to transmit Lyme bacteria?
CDC says a tick must be attached for more than 24 hours before the Lyme disease bacterium can be transmitted, which is why daily checks matter. See a clinician if you find an attached tick and have questions.
Where can I find my own state's dates?
Ask your state or county health department or your Cooperative Extension office, as CDC suggests. They hold surveillance data we cannot reproduce here. For mosquito specifics at home, see how to keep mosquitoes away in the backyard and mosquito-borne diseases in the US.
Lemon Eucalyptus Essential Oil
Lemon Eucalyptus Essential Oil from our own shop, in sizes from 0.5 oz to bulk.
From $9.99
Shop Now →