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Warmer winters: Here's what data shows about California's average temperatures since 1970

Data shows winter is getting warmer in California
Data shows winter is getting warmer in California 02:16

SACRAMENTO - Winter continues to be the fastest-warming season across portions of Northern California, according to a new climate report. Winter temperatures are warmer across the Sacramento and Central Valley compared to the past few decades. 

A report by Climate Central shows the average temperature since 1970 has increased more in the winter than any other season.

A warmer winter may have ripple effects on agriculture and state water supplies that rely on colder temperatures in December, January and February. 

California state climatologist Dr. Michael Anderson with the Department of Water Resources (DWR) said they have noticed the change with how little fog forms and sticks around. 

"One of the big things we don't see so much in the Sacramento anymore are the days of just heavy fog. As things have warmed, you get above that threshold where fog can form, all of sudden now you've got clear sky, and boy, the sun can heat up the place," Anderson said. 

Anderson added that sometimes the change can be very apparent or it can be something you notice over time, 

"You really have to look at how the average moves. Is it a little bit each day? If every day is just a little warmer, then nobody really notices that's happening. Or do we get those periods where it's just like, 'Wow, it's really warm today. It's 10-15 degrees warmer than it should be?' " Anderson said. 

In the Sacramento Valley, the average temperature in the winter has increased by more than 2 degrees. Temperatures in the Central Valley increased by at least 2 degrees from 1970 to 2022. 

Climate Central

It's a small change to some, but it may bring future impacts to different industries. 

Anderson said one of the biggest impacts will be to stone fruit (ie. plums, cherries, avocadoes) and crop production across the valley. 

"One of the things we actually see in parts of Northern California impact the stone fruit. They really need those cold hours to really help produce fruit. What you start seeing is your cherry tree is only producing fruit at a certain level of the tree because that's where the conditions are being met," Anderson said. 

Warmer air is not only noticeable across the valley but toward the mountains, too. Anderson said if we do not have cold air overhead, snow levels will be higher as storms move in and may cause a rush of water downstream. 

"Say the freezing level may jump to 13,000 feet, right? Well, then all of a sudden there's a whole lot of rain coming down at once but we don't really have a rivering system built for it," Anderson said. 

He said the DWR is now focusing on more ways to create room for more water by leaving extra space open in reservoirs and transporting more water underneath the ground to aquifers. 

As the 2022-2023 winter proved, we can still get just the right storm systems and cold air.

"As we saw last year, it doesn't mean it never happens. You can get the right conditions, and because the atmosphere is warmer, it can hold more water," Andersons said. 

The trend is not just happening on the West Coast but nationally. Winter (December, January, February) is the fastest warming season for 75% of 238 U.S. locations, according to Climate Central. 

Climate Central

Climate Central said the top five warming winters since 1970 were in Burlington, Vermont (7.1°F); Milwaukee, Wisconsin (6.1°F); Chattanooga, Tennessee (6.1°F); Concord, New Hampshire (6.0°F); and Green Bay, Wisconsin (5.7°F).  

The warming season is also reflected in the increasing number of winter days with temperatures above normal. Sacramento experiences 15 or more days above average. 

Climate Central

Anderson said if we keep warming at the scale we do, some farmers and industries may have to adapt and change. 

"You don't quite get the ability to have the same crops develop because you don't have the cold hours and well, that motivates a change into what does grow well here. Anderson said. "They may be longer seasons where it's more hiking, mountain-biking but a shorter season for skiing."

He said now is a good time to make adjustments and keep an eye on how the climate is changing. 

"Just a big motivator, pay attention to those weather forecasts right really be mindful and aware of what's going on," Anderson said.

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