Welcome to the forum. I'm hoping it's a mild/low grade fever? What's your temp?
My first inclination is to say you might have an infection or flu in addition to ulcerative colitis, as that is certainly possible. I did some searching on the forum here and others claimed to have mild grade fevers during flares, as you have. I found some other sites that claimed mild grade fevers are possible uc symptoms, certainly not the most common one. Nausea seems to be more common, some times to the point of throwing up.www.healingwell.com/community/default.aspx?f=38&m=2802317www.healingwell.com/community/default.aspx?f=38&m=2587444
Important though is severe fevers (especially combined with other symptoms) might be suggestive of emergency situations like toxic megacolon or a bowel perforation. Those require immediate, urgent care.