Unprecedented Humidity and Climate Challenges in Southern California

Southern California has long been known for its attractive, mild weather. Traditionally, the region’s climate has been described as a “mild Mediterranean-type climate,” drawing people with promises of healing warmth and fertile soil. Railroads promoted Los Angeles as a haven for the sickly, where rain was rare, and the heat was dry. This climate made headlines when it dared to deviate from expectations.

The current situation challenges this image. The region has recently experienced oppressive humidity, more reminiscent of Florida and the Gulf Coast. Many have remarked this as the most severe humidity they’ve encountered. Scientists, including UC’s climate expert Daniel Swain, identify this mix of high heat and tropical air as one of the worst humidity events modern Southern California has seen.

“These are some of the highest humidities we’ve ever experienced in coastal Southern California,” said Daniel Swain.

This weather pattern is not just a temporary anomaly. Climate change has been warming Southern California for years, increasing risks of fires and droughts. The anticipation of a strong El Niño winter could lead to significant damage along the coast. Swain warns of possible coastal flooding, beach erosion, and bluff collapses this winter, cautioning that solutions might be limited.

Record-Breaking Humidity

Before the week’s intense moisture, Swain’s assessments using August data showed this summer had the highest humidity in decades, based on dew points from several Southern California airports. Swain notes this year’s numbers surpass those of the last 46 years.

The National Weather Service defines comfortable humidity with dew points below 60. Tuesday saw dew points hitting 76 in places like Long Beach and Newport Beach, comparable to New Orleans and Orlando at that time.

This spike makes the heat more intolerable and threatens health. Coastal Southern California usually relies on factors like ocean cooling, mountain protection, and weather patterns that keep tropical moisture at bay, preserving its dry summers. However, these safeguards failed this summer.

As climate specialists note, when humidity rises, heat feels more severe. “This is not the same thing as you might say, ‘Yeah, Woodland Hills, they always get to 110 every summer,’” Swain explained, illustrating how humidity impedes the body’s natural cooling processes and makes even shaded areas feel warmer. Lack of air conditioning in some areas compounds these effects.

L.A. County health officials have urged residents to monitor for heat-related illnesses like dizziness and rapid heartbeat, emphasizing the dangers since heat causes more U.S. deaths annually than other natural disasters combined.

Causes for the Extreme Humidity

The remnants of Hurricane Marie contribute significantly to the extreme humidity, as Marie’s vortex funneled moisture into the region. This event ties back to an unusually active Pacific hurricane season, which scientists link to El Niño. This tropical moisture, paired with local monsoonal flows, exacerbated this summer’s storms and heat.

An extraordinary marine heat wave further boosts humidity. The National Oceanic and Atmospheric Administration’s tracker shows a widespread marine heat wave along California’s coast. Ocean waters from the Galápagos to Alaska are strikingly warmer.

“The sea level off the coast of Southern California is now six to 10 inches above average,” Swain noted.

Concerns About the Upcoming Winter

With recent coastal damage still fresh, forecasters predict more erosion soon. Warnings are in place for significant beach erosion, coastal flooding, and dangerous rip currents. These threats are fueled by elevated sea levels and wave energy, intensified by Marie.

Furthermore, the anticipated arrival of Kelvin waves could complicate matters. These waves, associated with strong El Niños, raise sea surface temperatures and sea levels. With super king tides expected, concerns for unprecedented flooding grow.

Global warming further aggravates conditions. Rising ocean temperatures and melting ice sheets cause sea levels to increase. As Swain points out, human-caused climate change affects regional coastal flooding by amplifying global sea-level rise.