"This is the first real cold spell," said President of California Citrus Mutual Joel Nelson.
The hard freeze is threatening crops like mandarins. That is why Nelson says growers are working aggressively to protect their fruits.
"Today they've been making sure the propane tanks are full the diesel tanks are full the wind machines are ready to operate."
Nelson tells Action News earlier in the day at around 4 p.m. many farmers ran water through the ground.
"That warms the ground and as that warm air rises from the water the wind machines keep that warm air down in the grove."
Hard Freeze Warning in effect for Thursday and Friday mornings for parts of the San Joaquin Valley. Cold can negatively impact people, animals, plants and pipes. More info here: https://t.co/MTleBbPyXB pic.twitter.com/ujUZvxBvJY— NWS Hanford (@NWSHanford) December 20, 2017
Those powerful wind machines cover between 10 to 12 acres and they help elevate grove temperatures about five degrees.
Growers are going through all possible steps to reduce the risk of seeing the damage.
"It cost roughly a few million dollars every night to protect this crop. It's a nervous time and we're hopeful that the industry can survive this."
But first, they must make it through tonight because Thursday night is expected to be worse.