Power has been lost in some areas while thousands of Fijians have been moved to evacuation centres for safety.
The storm hit the main island of Viti Levu on Monday, with winds exceeding 150 kilometres per hour.
Roads are blocked blocked and all flights have been grounded for the popular tropical destination.
The Joint Typhoon Warning Centre said Evan could generate 12 metre swells, creating major flooding concerns for authorities.
Evan has already caused widespread destruction in Samoa.
The Samoa Observer newspaper says up to four-thousand people were left homeless.
With files from CNN