The National Hurricane Center issued a tropical storm watch for the lower Florida Keys on Sunday evening as Tropical Storm Ian continues gaining steam in the Caribbean. 

Florida Gov. Ron DeSantis declared a state of emergency for the entire state on Saturday and urged residents to prepare for the storm. 

Tropical Storm Ian, which currently has maximum sustained winds of 45 mph, is expected to go through rapid intensification then become a major hurricane on Tuesday. 

Tropical storm Ian's trajectory into Florida.

A forecast shows tropical storm Ian intensifying into a powerful hurricane and hitting Florida on Thursday.  (Fox Weather)

It's projected to pass over or near the Cayman Islands and western Cuba on Monday, then enter the Gulf of Mexico on Tuesday. 

"You see while it doesn’t have an eye, you can see a very impressive twist, rotation in the clouds so that implies a lot of structure there," Jamie Rhone, the Acting Director the National Hurricane Center, told FOX Weather

"So when it moves into a more conducive environment, especially the northwest Caribbean where the oceans are very warm, it could rapidly intensify and all our guidance is showing that’s a high probability."

BIDEN CANCELS DNC RALLY APPEARANCE IN ORLANDO NEXT WEEK AS TROPICAL STORM IAN STRENGTHENS OVER CARIBBEAN SEA

Southern and central Florida are expected to see heavy rainfall on Thursday, Friday, and Saturday, while the Florida Keys could see flash and urban flooding through the middle of the week, according to the National Hurricane Center. 

Tropical Storm Ian

Tropical Storm Ian is seen near the coast of Cuba in this satellite image taken September 25, 2022.  (National Oceanic and Atmospheric Administration (NOAA)/Handout via REUTERS)

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It's too early to predict the storm's exact track after hitting Florida on the Gulf Coast, but it could move inland over the southeast or go up the East Coast. 

President Joe Biden also declared a state of emergency for Florida on Friday, authorizing the Department of Homeland Security and FEMA to coordinate relief efforts.