Multiple Weather Hazards Affect Southern California
Southern California is experiencing several weather-related hazards Thursday, September 24, 2026. The threats range from windblown dust and unhealthy particle pollution in Imperial County to flash flooding and thunderstorms across portions of Riverside County and the desert areas.
Residents and travelers should monitor official alerts closely because thunderstorms can produce sudden heavy rain, dangerous runoff, lightning and rapidly changing conditions.
Air Quality Alert for Imperial County
An Air Quality Alert is in effect for Imperial County this afternoon through this evening because of harmful particle pollution from windblown dust.
The alert covers portions of the Imperial Valley and surrounding areas, including El Centro, Calexico, Brawley, Salton City, Ocotillo and Plaster City. The Imperial County Air Pollution Control District issued the alert, with pollution levels potentially varying by location and weather conditions.
Windblown dust can reduce visibility and send fine particles into the air. Particle pollution can penetrate deep into the lungs, making conditions more concerning for people with respiratory or heart conditions.
Air Quality Safety
Residents should:
- Limit prolonged outdoor activity when dust levels are elevated.
- Keep windows and doors closed when practical.
- Use indoor air filtration if available.
- Avoid strenuous outdoor exercise during periods of heavy dust.
- Wear appropriate respiratory protection if exposure cannot be avoided.
- Motorists should slow down if blowing dust sharply reduces visibility.
Flash Flood Warning for Riverside County
A Flash Flood Warning was issued for Riverside County Thursday afternoon, with the National Weather Service reporting thunderstorms producing heavy rainfall.
The warning was in effect until 4:30 PM PDT, with rainfall rates estimated at 1.25 to 1.75 inches per hour. The National Weather Service described the threat as life-threatening flash flooding, with impacts possible along creeks and streams, urban areas, highways, streets and underpasses.
Areas specifically identified included portions of Highway 74 between Anza and Palm Desert and Highway 74 between Mountain Center and Anza.
Flash Flood Safety
Never drive through floodwater.
Water covering a roadway can hide washed-out pavement, debris or dangerous currents. Drivers encountering flooded roads should turn around and find another route.
People near washes, creeks and low-water crossings should move to higher ground if flooding develops.
Strong Thunderstorms Near Joshua Tree National Park
Strong thunderstorms are also affecting the desert region near Joshua Tree National Park and surrounding areas. Storms in this environment can produce sudden downpours, lightning, gusty winds and localized flooding.
Even areas that receive little or no rainfall can experience dangerous runoff from storms occurring upstream or nearby.
Visitors to Joshua Tree National Park should avoid washes and low-lying areas when thunderstorms are nearby and seek shelter from lightning.
Why Desert Thunderstorms Can Produce Dangerous Flooding
Desert terrain can make flash flooding particularly hazardous. Normally dry washes can quickly become channels of fast-moving water after intense rainfall.
Heavy rain upstream can also send water into an area after the storm has moved away.
For this reason, do not camp, hike or park in washes when thunderstorms are threatening.
Essential Safety Checklist
If you’re under a thunderstorm threat:
- Move indoors or into a substantial enclosed structure.
- Stay away from isolated trees and exposed ridges.
- Avoid washes and low-water crossings.
- Secure loose outdoor items when conditions allow.
- Keep weather alerts enabled on your phone.
If flooding begins:
- Move to higher ground immediately.
- Never walk or drive through floodwater.
- Avoid bridges and low-water crossings.
- Follow instructions from emergency officials.
- Remember that flooding can continue after rainfall decreases.
If dust becomes heavy:
- Reduce outdoor exposure.
- Close windows and doors.
- Slow down while driving.
- Use headlights during severely reduced visibility.
- Pull completely off the roadway if visibility becomes dangerously low.
Bottom Line
Southern California faces a combination of dust-related air-quality concerns, flash flooding and strong thunderstorms today. Imperial County residents should be alert for windblown dust and elevated particle pollution, while people in Riverside County and the Joshua Tree desert region should remain prepared for sudden heavy rain, lightning and flooding.
Turn around, don’t drown, and never underestimate a desert thunderstorm.
