FleaDates › Tick season › Pennsylvania
Northeast · PA
When are ticks active in Pennsylvania?
Ticks in Pennsylvania are typically active early March to early December, heaviest May–Oct — and adult blacklegged ticks can surface on any mild winter day.
Ticks to know in Pennsylvania
Pennsylvania is blacklegged tick country through and through — its wooded ridges and valley farm edges are among the most Lyme-heavy landscapes anywhere — with activity from early March to early December and the peak running May through October. American dog ticks are a steady summer presence in fields and along mowed paths, and lone star ticks are gaining ground in the southern counties. Adult blacklegged ticks quest on any mild late-autumn day, so a November dog needs the same going-over as a June dog.
Wherever the calendar sits this month, the habit that actually catches ticks is the after-walk check: ears, collar line, armpits, between the toes. Prevention plus checks beats either alone.
Month-by-month tick activity in Pennsylvania
| Month | Typical activity | Average temperature |
|---|---|---|
| January | Quiet | 31°F |
| February | Quiet | 32.9°F |
| March | Moderate | 40.7°F |
| April | Moderate | 51.9°F |
| May | Peak | 62.1°F |
| June | Peak | 71.1°F |
| July | Peak | 75.6°F |
| August | Peak | 73.9°F |
| September | Peak | 67.1°F |
| October | High | 55.6°F |
| November | Moderate | 44.9°F |
| December | Low | 35.9°F |
Estimates from NOAA U.S. Climate Normals (1991–2020), averaged across 4 weather stations near Pennsylvania's larger cities, using the ~40°F activity threshold reported in published tick research. Real years run early or late with the weather.
Fleas peak later. Pennsylvania flea season typically runs early April to early November — see the Pennsylvania flea season page.
Frequently asked questions
When does tick season start in Pennsylvania?
Around early March in a typical year, once temperatures clear roughly 40°F — noticeably earlier than flea season. A February thaw can bring ticks out ahead of schedule.
What ticks live in Pennsylvania?
The species dog owners most often meet in Pennsylvania: blacklegged (deer) tick, American dog tick, lone star tick. Pennsylvania is blacklegged tick country through and through — its wooded ridges and valley farm edges are among the most Lyme-heavy landscapes anywhere — with activity from early March to early December and the peak running May through October. American dog ticks are a steady summer presence in fields and along mowed paths, and lone star ticks are gaining ground in the southern counties. Adult blacklegged ticks quest on any mild late-autumn day, so a November dog needs the same going-over as a June dog.
Do I need tick prevention in winter in Pennsylvania?
Yes. Ticks overwinter under leaf litter and snow rather than dying off, and mild spells wake them — which is why veterinary organizations recommend year-round parasite prevention. The calendar shows when pressure peaks, not when protection can lapse.
What about fleas in Pennsylvania?
Fleas run on a warmer calendar — in Pennsylvania that's early April to early November. See the Pennsylvania flea season page for that month-by-month picture.