Cold temperatures in the Valley have citrus growers on high alert

As winter approaches and leaves shrivel, this is the time of year citrus ripens into vibrant colors and when growers like Nick Hill begin to lose sleep over their fruit.

"Most of my guys and myself will be up for the next 3 or 4 days all night long," Hill said.

Hill grows every type of citrus from grapefruit to navel oranges. He's worried most about his mandarins and lemons, bracing for this year's first moderate freeze.

"I base everything on 27 degrees, how long we are above 27 and how long we are below."

Forecasts indicate temperatures could drop to the mid-20s Monday and last for periods as long as three to five hours. Hill says anything more than four is worrisome.

Hours before sundown growers were already testing their wind machines and Hill started running water to warm the ground.

"It's all about combinations of water, when to turn everything on and when to stop everything."

A science that Hill has perfected over 35 years.

Growers say cold weather is not without benefits though. It is needed to toughen the fruit and help turn it into bright orange.