How Many Days Will You Need AC In Napa Valley This Summer?

NAPA VALLEY, CA — Residents of Napa Valley are not running their air conditioners more often than in the previous two decades to remain comfortable during hot summer days, according to an interactive map and analysis from The Washington Post.

But it’s going to get worse, according to projections for 2060. From 1981 to 2000, Napa Valley residents needed their air conditioners an average of 58 days. The number of days decreased by five from 2001 to 2022 but is projected to increase by 37 days by 2060.

In Napa Valley, here’s how heat indices and actual air temperatures have changed and are projected to change:

• 1981-2000: 58 summer days requiring air conditioning, with an average heat index of 67 degrees and average air temperature of 67 degrees.
• 2001-2022: 53 summer days requiring air conditioning, with an average heat index of 66 degrees and an average air temperature of 67 degrees.
• Projected for 2060: 90 summer days requiring air conditioning, with a projected average heat index of 72 degrees and air temperature of 72 degrees.

The analysis is based on the heat index, the feel-like temperature that combines the air temperature and relative humidity, rather than air temperature alone. A 65-degree Fahrenheit daily mean temperature was used to capture cooling needs throughout the day in cities nationwide.

The Post cited 2022 research in setting the 65-degree heat index threshold to determine air conditioning requirements. Any day surpassing that threshold was counted as a day requiring air conditioning for all locations annually, The Post said. The news outlet was assisted in the analysis by Colin Raymond, a UCLA research scientist. For the projected 2060 period, The Post used forecast air temperature and specific humidity from the NASA Center for Climate Simulation.

This year has so far been the hottest summer on record for millions of Americans from California to Maine as heat records fall around the country, especially in the U.S. Southwest as the world grows hotter with more greenhouse gasses added to the atmosphere.

Following a hot start to July in the Bay Area, the NOAA’s Climate Prediction Center forecast the odds for above-normal temperatures to be considerably lower in the Pacific Northwest and coastal California for the rest of the summer. In the Pacific Northwest, equal chances—EC — of above, near or below normal temperatures are forecast due to expected troughing during the month of July. There is also uncertainty about where temperatures will fall in coastal California, where equal chances are also favored due to below-normal coastal sea surface temperatures leading to the possibility of an enhanced sea breeze.

Some Of The Hottest Temperatures Worldwide Seen Over The Last 10-15 Years

Last Thursday, high temperatures set records in the North Bay cities of Santa Rosa (113), Napa (106), and Kentfield (112). These were among several Bay Area cities with record-setting heat last week.

Since record-keeping began, some of the hottest temperatures worldwide have been seen in the last 10 to 15 years. Randall Cerveny, a professor at Arizona State University, told The Associated Press the heat records are the clearest possible signal that humans are altering the climate.

In addition to the U.S. Southwest, Temperatures in India and the Middle East have been exceedingly hot this year, he said.

“It feels like the air is a blanket of just hotness that is enveloping you,” he said of the heat, which killed at least 37 people in the United States in July, CNN reported.

It’s been the hottest summer on record to date for around 100 US cities from Maine to California. Heat is suspected in the deaths of least 37 people in the United States in July, a number experts said is likely underestimated due to the amount of time it takes to attribute a death to heat, nature’s most prolific weather killer.

The Associated Press contributed to this report