Clearly there are many examples of symbolism in this excellent play, but one of the biggest to my mind is the storm that occurs in Act III whilst Lear is wandering itinerantly around the bleak heath. It is important to note how this storm functions symbolically in a number of different ways, depending on your own interpretation. Firstly, the storm could be said to be an external representation of Lear's inner turmoil, confusion, and growing sense of madness. Secondly, the storm could be said to represent the awesome powers of Nature, which in turn cause Lear to reflect upon his own mortality for the first time and gain a sense of humily. Consider the following quote from Act III scene 2 when Lear addresses the storm:
Then let fall
Your horrible pleasure. Here I stand your slave,
A poor, infirm, weak, and despised old man.
Facing the storm has helped Lear to humble himself and recognise his own identity, now that his daughters have taken his kingdom from him and have left him to wander alone. Lear also suggests that the storm may symbolise some sense of divine justice as Nature or God is angry at what has happened in the play.
Lastly, the storm may represent the political turmoil rather than personal turmoil that has swallowed up the Britain presented in the play. There is a definite sense of the old order of things coming to an end and chaos ensuing as a result.