What Causes A Delayed Menstrual Period?

I am a fit, heathly 18 year old, virgin (in every way) girl. My period is never late but now it is by three days. I was severly sunburned--fever, blistered, all that good stuff--a few days before I was supposed to start and I was wondering if that could delay my cycle. I did ovulate on schedule and I cannot think of any other possible cause. Please and thank you!