Hurricane Hilary intensified into a Category 4 storm on Friday morning, with forecasters warning that it could bring weather with “significant impacts” to the southwestern United States and Mexico over the weekend.

The National Hurricane Center said the storm had sustained winds approaching 140 miles per hour early Friday after becoming a hurricane a day earlier. Hilary is now expected to continue gathering strength throughout the day before rapidly weakening on Saturday and Sunday. It’s currently projected to make landfall near San Diego as a tropical storm on Monday if its current track is maintained, though rains are forecast to begin in the Southwest on Friday before reaching a peak from Sunday into Monday. It could become the first tropical storm to make landfall in Southern California since 1939.