(CNN) Deserts aren't supposed to get much rain, but Tropical Storm Rosa is flipping the script.

Rosa is expected make landfall Monday evening on Mexico's Baja California, CNN meteorologist Gene Norman said.

The storm will douse Baja California with 3 to 6 inches of rain, with some spots getting up to 10 inches, the National Hurricane Center said.

Evening satellite imagery shows weakening tropical storm #Rosa headed for Arizona. The moisture is coming and the forecast looks on track. Heaviest rain in northern AZ Monday night and Tuesday. See https://t.co/uqhCqBQZ4O for details #azwx pic.twitter.com/4cpGSelfHB — NWS Flagstaff (@NWSFlagstaff) October 1, 2018

As it moves northeast Rosa will also dump 2 to 4 inches of rain on much of Arizona, with up to 6 inches in the Arizona mountains.

Historically, it's unusual for the US Southwest to get pummeled by a hurricane or tropical storm. But "these events have begun to increase in recent years," Norman said.

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