Hurricane Polo's Moisture Drives a Flash Flood Threat Across the Southwest

Hurricane Polo came ashore over Baja California and pushed into northwestern mainland Mexico early Tuesday as a Category 3 storm. It had strengthened to a Category 5 at a record pace over the eastern Pacific before landfall. The bigger story for households in the United States is the deep plume of tropical moisture it is throwing north.

As of Tuesday, September 29, forecasters put the greatest flash flood risk over Arizona, New Mexico, Colorado, and the Kansas, Oklahoma, and Texas panhandles. Rain totals of 3 to 5 inches are expected across the Southwest, falling at 1 to 3 inches an hour. A few spots could see more than a month of rain in a single day. Those totals are the current outlook and are likely to shift as the moisture tracks north and east through Thursday. Flash flood warnings are already posted in parts of Arizona and southern California. Towns in Nevada, Arizona, California, and Utah saw flooding on Monday.

Flash flooding catches people off guard in dry country because hard, sun-baked ground sheds water instead of soaking it in, so a dry wash can turn into a fast channel within minutes. If rain is in your forecast this week, take a few minutes to review how to prepare for flooding before it starts. Know what surviving a flood asks of you once water is moving. Move to higher ground early. Never drive or walk into water crossing a road, because most flood deaths happen in vehicles.

The same tropical systems that flood the desert bring the coasts a yearly threat, so the habits that carry you through this week are the ones that keep you ready to be prepared for a hurricane too. Keep a few days of water within reach. Learn how to purify questionable water, since flooding can foul a tap or a well long after the rain stops. Polo will keep feeding moisture inland through Thursday, so check your local warnings before you head out, and stay ready rather than scared.