ORLANDO (CBSMiami/AP) — Farmers are preparing for a drastic drop in temperatures Monday night and Tuesday morning.

Some locations will feel the coldest air of the winter season.

READ MORE: CBS4 Nat Moore Trophy Profile: Miami Central High Safety Alfonzo Allen

Fern growers checked their irrigation systems to make sure they were ready to protect their plants against cold weather and shelters opened around the state as Floridians prepared for freezing weather.

A hard freeze warning was issued for the northern half of the state and extended as far south as Hernando, Lake, Sumter and Volusia counties. Emergency management officials warned that Monday night was expected to be the coldest night of this winter season, and record-low temperatures were expected to be broken in north Florida.

Temperatures were expected to get as low as the upper teens in north Florida, with the wind chill making it feel as cold as zero degrees. Freezing temperatures in north Florida could last for 18 hours overnight Monday and into Tuesday, as well as another 15 hours from Tuesday night into Wednesday.

In central Florida, low temperatures were expected to be at or around freezing for up to eight hours overnight Monday and into early Tuesday. Temperatures also were expected to dip below freezing Tuesday night.

Temperatures were forecast to be in the upper 30s in South Florida overnight.

“It is the duration of these freezing temperatures into the late morning and early afternoon in some places that make this weather event so rare,” deputy state meteorologist Tiffany Hersey wrote in an email.

In Pierson, an area that bills itself as the fern capital of the world, growers were preparing to use their overhead irrigation systems as protection against the cold. They planned to spray their plants to create a protective ice layer once the temperature reached freezing and then run a constant flow of 72-degree water over the iced plants. The freeze was occurring at a particularly important time of the year when the current crop of ferns will be used for Valentine’s Day bouquets.

“We’re all concerned,” said fern grower Samuel Bennett. “As a grower, you always hope that perhaps it won’t be as extreme as predicted, but you have to be prepared to protect your crops.”

Florida’s citrus crops, which are grown in the southern half of the state, weren’t expected to be in jeopardy given that damage occurs only if the temperature is 28 degrees or lower for more than four hours or more. But citrus trees in low-lying pockets could be vulnerable since temperatures tend to be colder there than in surrounding areas.

“We are cautiously optimistic we can get through in good shape,” said Andrew Meadows, a spokesman for Florida Citrus Mutual, a grower’s group.

Most of Florida’s other vegetable and fruit crops are grown in the southern half of the state and weren’t expected to be at risk, although growers were concerned about strawberries grown west of Tampa, where a freeze warning was in effect.

READ MORE: Arrest Affidavit: Accused Hollywood Cop Killer Jason Banegas Claims He Was Trying To Kill Himself In Struggle With Slain Officer Yandy Chirino

Meanwhile, cold weather shelters were opening up from St. Petersburg to Pensacola.

At the Water Front Rescue Mission in Pensacola, which ordinarily serves just men, the shelter was opening its doors to women and children during the next two nights. The shelter can accommodate about 250 men and perhaps another 100 women and children, said Mick Breault, president of Water Front Rescue Mission.

“We will open our doors to everyone until we fill up,” he said.

Breault said he was especially concerned about people living in homes without gas or electricity for heat. Because the region rarely gets seriously cold, some people opt to go without the utilities, he said.

“People can start fires trying to get warm,” he said.

Shelter workers were going to areas frequented by the homeless in vans to try and to encourage people to come back to the shelter.

“We know a lot of them won’t go, but we are going to try,” he said. “When it is this cold, some who normally wouldn’t go might change their minds.”

Homes in the Pensacola area were not designed for extreme cold, said Adam Nelson, owner of All Pro Plumbing and Drains Inc. in Pensacola.

Sprinklers systems are often placed at a very shallow depth in the yard and that makes them susceptible to freezing and breaking, Nelson said, and a lot of the plumbing in homes in the area is uninsulated.

Nelson recommended that faucets be left running to prevent pipes from freezing and that homeowners place insulation over any exposed outdoor pipes.

“I know we will be slammed tomorrow morning,” Nelson said. “We will have more calls than we can handle.”

MORE NEWS: Parkland Survivor Anthony Borges Prepares To Be In Court For Plea Hearing

(TM and © Copyright 2014 CBS Radio Inc. and its relevant subsidiaries. CBS RADIO and EYE Logo TM and Copyright 2013 CBS Broadcasting Inc. Used under license. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed. The Associated Press contributed to this report.)