Everyone's probably heard the thoughts floating like clouds analogy. I would say it's more like a slight mist.
However, this morning before sitting Zazen I would compare it to some thing like a Mack truck hitting me dead on, flinging me to the ground and thus continuing to crunch my skull under it's wheels, dirtying it's mudflaps, and driving away merrily leaving me there on the road to ponder big questions like "Why am I lying on the road with half of me over there, and.... I don't even know where my shoes are!"
But it's ok now. Don't worry. I'm alright.