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Southern California Swept by Tropical-Level Humidity in Heatwave

Ocean warming, a heat dome and El Niño combined to drive unusually high moisture into the region leading to extreme stickiness even as forecasts call for cooling to begin Saturday.

Overview

  • Humidity peaked this week, with dew points near 70–73°F in downtown Los Angeles and readings as high as about 81°F near the Salton Sea on Thursday.
  • Several local stations set or broke daily high-temperature records during the same heatwave, including Downtown L.A. at 98°F, Woodland Hills at 111°F and Lancaster at 107°F.
  • The National Weather Service kept extreme heat warnings and red flag fire warnings in effect while Los Angeles opened hundreds of cooling sites for residents without air conditioning.
  • Forecasters say the stickiness stems from a warm Pacific that is evaporating more water, a heat dome pulling tropical moisture north, and early El Niño influences, and they expect temperatures to fall starting Saturday.
  • The combination of high overnight lows and elevated humidity raises heat-illness risk for older adults, children and outdoor workers and keeps fire danger high if storms produce dry lightning or winds spread any blazes quickly.