Backstreet Boys -- Christmas FRAUD in November

It's barely November ... but the Backstreet Boys are already pretending it's Christmas time.

The entire band -- even Kevin -- threw on their obligatory ugly winter outfits for a performance of their new Christmas song at Disneyland this weekend ... sparkly sweater, checkered jacket, scarf, etc.

For the record, it was 94 DEGREES in Anaheim yesterday.

We're told the performance was pre-recorded for an upcoming Xmas special.