In Chichester celebrations have been scaled back and will no longer feature live entertainment or a market.
Weekend events are scheduled in Burgess Hill, East Grinstead and Rye, and organisers hope they will still be able to continue.
Burgess Hill Town Council has moved many of its stalls and performances indoors for its Saturday event.
Performances that were due to take place outdoors will now take place in Market Place Shopping Centre, while stalls have moved into Cyprus Hall.
Organisers said: “Thanks to the incredible support from our local community partners, staff, and councillors, we’re still able to adapt and deliver a wonderful event for all.”
In East Grinstead, the Big Reveal event, where more than 60 shops will unveil their Christmas window displays, will still go ahead, though some events have also been moved indoors.