The remnants of Rosa could bring as much as a year's worth of rain to desert areas such as California's Imperial Valley and Arizona's Yuma County - both significant producers of vegetables for the nation.
Rosa was creeping northeast Sunday morning as a Category 1 hurricane, with sustained winds of 75 miles per hour, according to the National Hurricane Center. Rosa was expected to reach Baja California on Monday as a tropical storm.
The hurricane center said there were no coastal watches or warnings in effect, but swells generated by Rosa were expected to cause risky surf and rip current conditions along portions of southwestern Mexico, the peninsula and southern California.
It's then expected to move quickly northwest as it weakens.More news: $1249 iPhone XS Max costs Apple $443 to make
Forecasters warned that swells generated by Rosa will affect portions of the southwestern Mexican coast and southern Baja California into the weekend, causing life-threatening surf and rip current conditions.
Forecasts call for heavy rainfall in the watch areas, which include Las Vegas, Phoenix and Salt Lake City, with possible flooding in slot canyons and normally dry washes and a potential for debris flows from recent wildfire burn scars.
Meanwhile, Tropical Storm Sergio was growing in the Pacific and could become a hurricane force later Sunday or early Monday, though it posed no immediate threat to land.
Forecasters expected the storm to drop between 3 inches to 6 inches in Baja California and northwestern Sonora with isolated totals up to 10 inches.