It really IS fall

We have locust trees outside our office building and they are the first to turn yellow and fall off of the trees.  They are also small enough that they stick to our shoes and there has been a trail of leaves into the building for a couple of weeks now. But today I noticed that the walkway was covered.  We have turned a corner and fall is here.  The rest of the trees are just starting to turn, but I checked to make sure that our furnace is working because it's supposed to get cold.