Freezing temperatures over the next few nights will have Yumans reaching for blankets and coats — for themselves and for their plants.
A cold snap is expected to swoop in later Thursday, bringing below-average daytime highs and nighttime lows in the low 30s. Also, a stiff breeze from the west should usher in the dry cold streak, said Dave Samuhel, a meteorologist with www.accuweather.com.
“That west wind will kind of be bringing that cold air in.”
Thursday's high is forecast at a mild 68 degrees (the normal is 69) with winds of up to 25 mph into the evening, according to Accuweather forecasts. By Friday, the wind should mellow some but days will turn noticeably cooler, ranging from 53 to 56 degrees through Tuesday.
The nights will be cold. Just how cold depends on who you ask: Accuweather is putting the lows between 34 and 39 between Friday and Monday nights. The National Weather Service predicts 31 through 35 degrees. And the University of Arizona-Yuma, which provides growers with detailed freeze forecast maps two days in advance of freezing temperatures, predicts lows in the 20s by early Friday morning — at least a foot from the ground, such as where the lettuce heads are.
Additionally, the NWS has issued a freeze watch for the area from late Friday night through Tuesday morning, and a wind advisory for Thursday afternoon and evening owing to potential gusts of up to about 45 mph.
For growers, harsh cold means protecting valuable produce. Kurt Nolte, executive director of the Yuma County Cooperative Extension, said agriculture professionals aren't unprepared for winter's coldest snaps.
He said lettuce growers may, if they can, water their fields. Because the water, coming in from the Colorado River, is about 45 degrees and thus warmer than the air, it will release some of its heat and, sort of like a liquid blanket, protect the leaves from significant damage. Even three inches of water could be enough to do the trick, he said.
For lettuce that's hours from being harvested, workers may cover the crops in black plastic. This allows the sun to hit the dark cover and prevent the formation of “lettuce ice,” which makes leaves very fragile and susceptible to damage if touched.
Citrus, which is less hardy than lettuce, may also benefit from being watered before the cold nights. Then, using the principle that heat rises, growers may run wind machines to push the rising warmth back down on the fruit, Nolte said.
For home gardeners, Nolte suggested bringing potted plants inside — just the garage is fine — or covering them with burlap, blankets or tarps. Native plants should be sturdy enough for the fluctuations, but non-native species like ficus trees can be hit hard, as can perennials like geraniums.
While it will be chilly for the next few days, from an agricultural perspective, at least, Nolte isn't predicting anything too bad.
“I don't see a catastrophic sort of freeze like the one we had a couple years ago,” he said, when a cold snap brought temperatures in the teens.
Hillary Davis can be reached at email@example.com or 539-6857. Find her on Facebook at Facebook.com/YSHillaryDavis or on Twitter at @YSHillaryDavis.