Labor Day weekend saw an early arrival of autumn rain in Southern California, bringing a temporary cooldown. However, just as the storms passed, scorching heat made a comeback on Tuesday. The temperatures are expected to remain above 90 degrees Fahrenheit until Friday. In eastern Los Angeles County, the highest temperature on Wednesday is expected to exceed 100 degrees Fahrenheit. In addition to the high temperatures, the unusual humidity levels pose greater health risks to the public.
On Wednesday and Thursday, residents may feel even hotter than the actual temperatures due to the increased humidity caused by the recent rain. The moist ground quickly raises the humidity in the lower atmosphere under the scorching sun.
A short-term summary issued by the National Weather Service (NWS) Los Angeles/Oxnard office on Tuesday afternoon shows that the increase in temperatures and humidity in the region will cause moderate to severe impacts, primarily concentrated in coastal and valley areas, expected to last at least until Thursday.
According to meteorological forecasts, the high-altitude high pressure will peak early on Wednesday morning. With weaker offshore pressure gradients, Wednesday is expected to be a hot day. Beach areas are expected to reach over 90 degrees Fahrenheit, while inland areas could reach 108 degrees Fahrenheit.
Even the usually cool Santa Monica Beach will see temperatures rise to 90 degrees Fahrenheit on Wednesday. Forecasted temperatures for the day include the Los Angeles Basin ranging from 91 to 100 degrees, coastal areas between 80 and 90 degrees, the San Gabriel Valley between 96 and 100 degrees, and inland areas potentially exceeding 90 degrees.
By Thursday, the high altitude high pressure will weaken, leading to a slight drop in temperatures. The highest temperature in Los Angeles is expected to drop by around 5 degrees. Thursday night temperatures are expected to range from 60 to 70 degrees Fahrenheit, while the dew point temperature influenced by Hurricane Marie may reach 65 to 75 degrees Fahrenheit. Human comfort levels decrease as the dew point temperature rises above 18 degrees Celsius, with humidity causing feelings of discomfort and heat when surpassing 21 degrees Celsius.
The high temperature risk warning map released by the National Weather Service shows that from Wednesday to Thursday, Southern California will experience widespread high temperature risks, with some areas facing extreme risks. The high temperature warnings for these two days have been upgraded to “extreme high temperature warnings.”
On Tuesday afternoon, coastal cities in Southern California, including Long Beach, Huntington Beach, Newport Beach, experienced dew point temperatures reaching 76 degrees Fahrenheit. Climate scientist Richard Thompson told the Los Angeles Times that the current humidity levels are approaching the highest values for the entire local year.
Such high humidity levels could result in heat stress and heatstroke risks. Symptoms of heatstroke include heavy sweating, muscle cramps, dizziness, and confusion, whereas heat stress symptoms include dizziness, headaches, dehydration, and fatigue.
As the heatwave continues, many people may seek relief at the beach. However, officials from the Los Angeles County Department of Public Health urge the public to refrain from swimming at this time.
The department has extended the “Ocean Water Quality Rain Advisory” for all beaches until at least noon on Thursday. Due to the season’s first rain in the past few days, pet waste and other debris accumulated on land have been washed into the ocean, leading to a surge in bacteria levels along the coast, exceeding California health standards.
The Department of Public Health explains that exposure to seawater before the advisory is lifted can result in illnesses, posing greater risks to children, the elderly, and vulnerable populations. Swimmers are advised to avoid contact with seawater in designated beach areas until the danger subsides.
The Los Angeles County Department of Public Health also advises the public to drink plenty of water, stay indoors in cool environments, and never leave children in cars. Residents without air conditioning can seek relief in air-conditioned places like libraries or cooling centers. For cooling center locations near you, visit https://ready.lacounty.gov/heat/ or call 211.
The forecast indicates that by Friday, the highest temperatures across all regions of Southern California will drop by at least 4 to 8 degrees Fahrenheit, significantly reducing the risk of heat-related illnesses. ◇