Seasonality
for Cat Flea
A pet can pick up fleas in any month, but the size of the problem swings with the season. As spring warms into early summer, the heat and humidity larvae need push populations upward — when most homeowners notice a flare-up. Indoors a heated, humid house keeps conditions favorable through winter, so an established infestation can persist year-round. Source: http://ipm.ucanr.edu/PMG/PESTNOTES/pn7419.html