Los Alamos County

Monsoon season in New Mexico starts in June and lasts through mid-September. It is characterized by heavy to severe downpours, lasting anywhere from five minutes to an hour. Such downpours can create a phenomenon known as flash floods.

Flash floods are just that; intense, short-duration floods. Usually they abate an hour, but can last as long as 24 hours. They occur throughout the southwest, and generally start high up in a mountain or canyon. Rain torrents follow the path of least resistance, initially canyons and arroyos. But along the way they pick up speed and debris. They can roll boulders, destroy footbridges, and uproot cottonwoods and piñons.

• Check the daily weather forecast when making plans to be outdoors. See the sidebar topics under Emergency Management and click on the link for Fire & Flood Alerts.
• When planning hikes or other trips into the mountains, stay alert to the possibilities of flash flooding if severe weather threatens, especially during the afternoons when showers are most likely – keep others informed of your plans. A good rule of thumb: if it starts to storm, hike to high ground! You do not want to be in a canyon, arroyo, or wash in a heavy rainstorm.
• Just because it isn’t raining where you are doesn’t mean you aren’t in danger. If you are below the storm in any way, floodwater and debris could be upon you within minutes.
• Keep pets and children out of canyons and arroyos during the monsoon season – warn children of the dangers of playing in or near canyon streams and arroyos when it storms.
• Never walk or drive through floodwaters of any depth – you don't know if the road underneath is still there. Find a safer route or wait until floodwaters subside completely. Six inches of fast-flowing water is enough to sweep you off your feet. Two feet of flowing water can float away most cars.
• If flooding occurs in your neighborhood, please remain calm and shelter in place. While some sections of town may become isolated for a time, flash floods recede quickly and access will be restored soon. It is essential that nobody panic, attempt to cross running waters, or enter unsafe areas.
• Keep in mind that flash floods are high-intensity but short-duration events. They seldom last longer than one hour. Even if some areas are temporarily isolated, emergency responders will be monitoring the situation and standing by to lend assistance as soon as possible.

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