SAN DIEGO — What started as a tropical storm off the Pacific coast of Mexico intensified into a hurricane Thursday, the National Weather Service announced.

Dubbed Hurricane Hilary, weather officials confirmed the strong storm system as a Category 1 Hurricane early Thursday and then upgraded it to a Category 3 hurricane later in the evening.

The storm is expected to move north along the Baja coast before potentially reaching San Diego County this weekend or by Monday, NWS explained.

What can be expected?

The region’s mountains, inland valleys and deserts can anticipate a lingering heat wave into Friday with isolated thunderstorms possible across the mountains and high desert, according to weather officials.

In a video statement Wednesday, NWS officials said “the door is open, the monsoon flow is here.” This means there’s a potential path for this hurricane to come right up the coast, though Hilary is expected to to weaken as it approaches the peninsula.

That doesn’t mean, however, that the remnants of the storm won’t be felt. An increasing “offshore flow wind” could create large swells and high surf come Saturday, said NWS.

The first heavy rains bands are also likely to occur on Saturday with increasing moisture to become widespread into Sunday, weather officials explained. Some of those rainstorms and thunderstorms could last until Monday.

Here’s a look at the rainfall outlook across San Diego County from Saturday, Aug. 9 through Monday, Aug. 21, based on NWS predictions:

Overall with the offshore flow, NWS says moderately cooler temperatures can be expected this weekend once the rain and clouds move in.

The lingering question for some: what’s the potential for San Diego experiencing tropical storm force wind? In short, NWS says there is a possibility of sustained winds reaching 40 mph or higher along the coast.

Boaters are now making contingency plans as the storm tracks north.

“I knew there were some winds and rains coming, but I didn’t realize there was a hurricane,” said Colby Smith, a local small craft boater.

While the prospect of a hurricane is concerning, Pat Abbott — a professor at San Diego State University — says San Diego might fare a little better than Baja California.

“The colder waters offshore are going to suck a lot of energy out Hilary. So hurricane, highly unlikely — tropical storm, good possibility,” said Abbott.

FOX 5’s Jaime Chambers contributed to this report.