Thankfully, the effects depicted in films are exaggerated in both magnitude and speed. You do not, in fact, instantly freeze or explode—heat transfers too slowly for that. Nor does your blood immediately boil, thanks to the resilience of your cutaneous system. You do not immediately fry to a crisp by unadulterated solar radiation, though you will get one hell of a sunburn. No, no, you have good ten to fifteen seconds with which to freak the fuck out before you begin to black out, and a solid two minutes or so before you fully expire.
Really interesting article on one of sci-fi’s favourite method of demise. The article also includes some pretty terrifying accounts of some of the more factual occurrences.