MEXICO CITY: Tropical depression Rosa made landfall on Mexico's Baja California peninsula Monday, dumping heavy rains on the Pacific Coast and threatening the southwestern United States with flash flooding, officials said.
Once a Category 4 hurricane, Rosa weakened as it approached land but still had the potential to dump up to 25 centimetres (10 inches) of rain on Baja California and five to 15 centimetres (two to six inches) on the US state of Arizona, said the US National Hurricane Center.
The rest of the western US also faced heavy rain across a broad swath of territory.
"These rainfall amounts may produce life-threatening flash flooding. Dangerous debris flows and landslides are also possible in mountainous terrain," the National Hurricane Center said.
Mexico's National Meteorological Service said Rosa had weakened to a tropical depression by the time it hit land, with winds of 55 kilometres (34 miles) per hour.
It was moving northwest at 17 kilometres per hour.
There were no immediate reports of damage or casualties.
Mexico's Pacific coast had already been hit hard by heavy rains before Rosa arrived.
At least 12 people died in flash floods in the states of Michoacan and Sinaloa. Another eight are missing.