At a moment's notice the firefighters could be rushing to one chilly canal or river near you. The temperature alone at this time of year is almost paralyzing.
"The canals and the river are both bitter cold. And if you were to fall in one of those about the first thing that would happen is you would get this sudden adrenaline rush and suck in air just because it's like being hit with a blast of an icy blast of air and that's actually how a fair number of people drown," said Bob Van Tassel of the Fresno Fire Department.
Changing water levels mean hazards are changing too. Trash, trees and rocks are big concerns.
"They could be safe with one water level and then very dangerous with the next water level the next day," said Kathy Curtice of the Fresno County Sheriff's Department.
Local rescuers expect a busy year. Last year, Fresno Firefighters responded to 31 water rescues and Cal Fire 17.
Rescuers trained to survey the water's features say all too often they arrive on scene to find people pushing their limits in conditions they clearly didn't expect.
"It looks relatively easy to get out there on some of the little islands and rocks like from here I can see a little of the shore, the water or the bottom of the river right here," said Curtice.
Crews say most life threatening mistakes happen after swimming out to a destination and becoming too exhausted to make it all the way back.