Lightning:
Make a Parallel Process event. Have it with some sort of Wait Frames thing, and then do a flash screen command. Put a Lightning Sound Effect around that too. Also, a Weather Effect of Rain wouldn't hurt. :>
Fire:
This requires a little more eventing, but it'll probably end up with something like some picture overlay...There was a tutorial on such lighting lying around here...I think...I'll find it.
http://forum.chaos-project.com/index.php/topic,1341.msg30068.html#msg30068Sure, it's used in a different situation, but the premise is similar...I think. It'll be a bit hard to understand since the pictures are removed...but oh well.
Alternatively, you can find a Lighting Script. Near Fantastica made one, for example (Though it'll probably require the dreaded SDK).