The western part of the county, including Roseville, Rocklin, and Lincoln tend to see the highest levels of mosquito and West Nile virus activity during the summer months. In the early winter and spring, ticks are most abundant, including those that carry Lyme disease.
The Gold Country
Mosquito season begins in the spring with the aggressive treehole mosquitoes. Ticks are prevalent in the late fall, winter, and spring months, especially those that carry Lyme Disease and other tick-borne illnesses.
The High Country
Mosquito populations are abundant in the spring and early summer as the snow melts. While the more common ticks found at lower elevations tend not to be a problem here, soft-ticks that commonly live in rodent nests inside structures can transmit diseases to humans.