This scene opens with an iconic image: Lear, a white-haired man, stands on a heath in the middle of a thunderstorm yelling at the sky. "Blow winds and crack your cheeks! Rage, blow!"
The Fool begs Lear to find shelter, but the King refuses; he would rather face the relentless elements than his ungrateful children.
Kent shows up, still disguised, and tells Lear he has to find shelter.
Lear keeps trying to drown out the thunder with his condemnation of the world's crimes. "I am a man more sinned against than sinning," Lear cries out.
Finally, Kent manages to maneuver him towards a hovel that will provide some shelter against the rain.
"My wits begin to turn," Lear mutters. But he has enough clarity of mind left to comfort his shivering Fool. Lear says, "Poor fool and knave, I have one part in my heart that's sorry yet for thee."
The Fool sings a little ditty (which sounds a whole lot like the song Feste sings at the end of Shakespeare's play Twelfth Night) and Lear and Kent seek shelter.
The Fool delivers a witty speech predicting that Britain will "come to great confusion" when priests are corrupt, beer-makers water down their beverages, when pickpockets stop preying on large crowds, and when "bawds and whores" build churches. In other words, these things happen all the time so, Britain has already fallen into decay. Get it? The Fool also predicts that, in the future, Merlin (the legendary wizard in King Arthur's court), will make this very same prophecy. (Note: Lear is set in ancient, pre-Christian Britain, long before King Arthur's reign in the sixth century, so Shakespeare's making a little joke about time here.)
Brain Snack: The Fool's "prophesy" is a parody (spoof) of "Merlin's Prophesy," a poem that was falsely attributed to Geoffrey Chaucer in George Puttenham's famous book called The Arte of English Poesie (1589). In other words, Shakespeare's giving a literary shout-out here.