Heavy rain in February left pools of water in gutters, potted plants, and even old tires, places where mosquitoes can breed.
Then weeks of warm weather created an even more friendly environment.
Aaron Devencenzi from the San Joaquin County Mosquito and Vector Control District says the conditions have brought out mosquitoes early.
"We had a trap that came in with several thousand mosquitoes in it, which is fairly early for this time of year to see that many," says Devencenzi.
Devencenzi says one of the main concerns in controlling the mosquito population is the spread of the West Nile Virus.
"Last year we had a record number of mosquitoes showing up in the air, and we had a high West Nile Virus even though there was less water last year," he says.
Devencenzi warns homeowners that anything that can hold a half an inch of standing water for more than five days can be a breeding ground for mosquitoes.