I have had Bronchitis for the past week?

and the doctor prescribed antibiotics and cough syrup. Well today since it is freezing and ugly weather in Texas, I started feeling different, chills and all. Got home tried my temp and it is at 101..called my doctor and she says to come back in tomorrow....why would I get a fever now being on antibiotics? Thank in advance for answering my question and what are some things I should look out for or do.