Symbolism of Storm
Shows the similarities of the physical storm that is raging outside, and the mental "storm" that shows the disorder and chaos that is occuring in King Lear's mind.
Significance - the consequence of turning his back to shelter ... which also adds to the fact that King Lear's mental state is in chaos where he rejects further shelter that Kent and teh fool try to persuade King lear to go into.
well, that's just my interpretation. don't take my word on it.