FleaDates › Flea season › Missouri › St. Louis
St. Louis · MO
When does flea season start in St. Louis?
Flea season in St. Louis typically runs late March to mid-November, peaking May–Sep.
Ticks in St. Louis
Local tick activity typically runs mid-February to early December, heaviest Apr–Oct. The species to know in Missouri: lone star tick, American dog tick, blacklegged (deer) tick.
More on species and timing: Missouri tick season.
Numbers come from NOAA U.S. Climate Normals (1991–2020) recorded at ST LOUIS SPRT OF S L AP — a climate-based estimate; real years wobble.
Frequently asked questions
When does flea season start in St. Louis?
Around late March in a typical year, once local averages hold around 50°F. A warm spring pulls it earlier — prevention shouldn't wait for the calendar.
Is flea season in St. Louis different from the rest of Missouri?
Not meaningfully — St. Louis tracks the Missouri statewide estimate closely. Both are climate-based estimates, so treat the edges as fuzzy, not exact.
Do dogs in St. Louis need prevention outside flea season?
Yes — vets recommend year-round parasite prevention regardless of the local calendar. Indoor fleas ignore the weather entirely, and ticks in Missouri are typically active mid-February to early December, a longer window than fleas get.