The Southwest Monsoon season occurs annually from June 15 to Sept. 30 and begins with a large-scale shift in winds that transport humid air to dry desert locations. Afternoon and evening thunderstorms during this time produce 40-50% of this region’s annual precipitation. Hazards produced from these thunderstorms include downburst winds, dust storms (haboobs), and flash flooding.
Damaging winds and downbursts
What is a downburst?
Strong winds within the rain-cooled downdraft of a thunderstorm.
What to do when winds are expected:
• Move indoors to an interior room.
• Watch for falling trees, flying debris, or downed power lines.
• Secure loose outdoor furniture and garbage cans, or move them indoors to prevent them from blowing away.
Wind speeds can exceed 40 mph and may go up to 100 mph.
Dust storms (haboobs)
What is a haboob?
A fast moving wall of dust that is the result of strong thunderstorm outflow winds.
What to do when driving in a haboob:
• Pull over away from the road.
• Turn off vehicle.
• Engage the emergency brake.
• Take foot of the brake pedal.
• Never stop in a traffic lane.
Avoid driving in dust storms at all costs.
Watch: maintain situational awareness and look out for signs of a potential thunderstorm.
Remember: if you can hear thrunder, you are probably close enough to be struck by lightning.
Get inside: most lightning strikes occur outside, so find shelter inside of a house or vehicle. If no shelter is available, get as low to the ground as possible.
Stay away: distance yourself from water, tall trees, telephone poles and any metal rails.
Lightning is the most unpredictable characteristic of monsoon storms.
What is a flash flood?
A rapid and extreme flow of high water into a normally dry area.
Driving in flash floods:
• Driving in floodwater is extremely dangerous.
• Water levels rise quickly and can fill the streets.
• Floodwaters can easily sweep a vehicle away in seconds.
• When coming across a flooded road, simply stop and turn back.
Never drive, ride or walk through floodwater.