While people are able to bundle up to weather the elements, zoo animals may be a bit more vulnerable to the cold temperatures.
Curators at the Fresno Chaffee Zoo take extra precautions to keep the animals safe and comfortable.
While visitors brave the colder temperatures, so do the animals.
"For some of our other animals, like our giraffes...if it's really cold out at night, we'll bring them in and actually lock them in their barns so they won't have the chance to get out into the cold, and they'll be warm the entire evening," said Mark Halvorsen with the Fresno Chaffee Zoo.
The type of care depends on the region where the animal comes from.
At the Sea Lion Cove, heated rocks provide the sea lions comfort, but their blubbery coats allow them to generally do well in the cold.
Other animals need to borrow warmth from infrared lighting, warming pads, hay, or heated barns.
Friday afternoon, an orangutan kept warm by hiding under a blanket in the sun.
But overnight, zoo staff will walk around the grounds to monitor the animals for signs of distress.
"To make sure that no one's showing any kind of signs of hypothermia, which include isolating themselves from the group, shivering, not being very active, and then we'll make provisions to either get that animal inside or add more heat to the area," Halvorsen said.
Perhaps those in the Reptile House are the luckiest; they're kept under heated lamps, indoors at all times. The cold-blooded animals can't generate their own heat.
Temperature is a concern all year round for zoo animals. The staff adjusts their care depending on the season.