Southern California has been feeling more like Florida this summer, not just hot, but noticeably muggy. Forecasters attribute the region's punishing humidity to a confluence of factors, including remnants of Tropical Storm Iselle, unusually warm ocean temperatures, a marine heat wave, a powerful El Niño, and the broader effects of climate change. This has made an already intense summer of heat particularly miserable, setting new records in some areas.
Dew points in the Los Angeles Basin have been consistently high, hovering around 70 degrees in many places. Coastal spots like Redondo Beach and Torrance even reached between 73 and 75 degrees on a recent Friday, according to Ryan Kittell, a meteorologist with the National Weather Service in Oxnard. For perspective, the Orlando International Airport recorded a dew point of 72 degrees that same afternoon. The weather service considers values above 70 degrees to be very humid and uncomfortable, with anything over 75 degrees feeling oppressive. Farther south, a weather station along the western shore of the Salton Sea in Imperial County registered a dew point of 81 degrees.
This unusual moisture has led to some significant weather milestones. State climatologist Michael Anderson, analyzing data from Oregon State University, found that Los Angeles recorded a monthly average dew point of 63.9 degrees last month. This figure is second only to July 2003's record of 64.4 degrees, as reported by California Department of Water Resources spokesman Jason Ince.
The humidity has also driven record-high overnight temperatures across Southern California. Numerous cities, including Burbank, Long Beach, Anaheim, Riverside, and Palm Springs, broke daily minimum temperature records. Palm Springs, for instance, saw an overnight low of 90 degrees, surpassing its 2011 record of 89 degrees. Kittell explained that water content in the air acts "like a blanket" that traps heat near the ground, preventing the typical nighttime cooling. He noted that water vapor is actually "the most potent and efficient greenhouse gas."
This lack of nighttime reprieve is exacerbating the risk of heat stress and related illnesses, according to Sam Zuber, a meteorologist with the National Weather Service in San Diego. She emphasized that it's these "overnight lows not cooling off like they should" that are currently driving heat impacts. The sea surface temperature at the Scripps Pier in La Jolla reached 76.8 degrees, approaching a daily record set in 2015. Alexander Gershunov, a research meteorologist at the Scripps Institution of Oceanography at UC San Diego, points out that ocean heat waves are becoming "more frequent, more intense and longer-lasting" due to global climate change. He added that while El Niño is a natural pattern, it is occurring "in an unnaturally warming world," contributing to increased evaporation from hotter oceans and, consequently, higher humidity levels, especially along the coast.
