The cooler weather means the local hairy-tailed moles have to dig deeper to keep up with the worms and grubs that comprise the bulk of their diet.
So they are forced to expand their summer “digs”– but what to do with all that excess dirt?
They have to push it out on the surface, which is why the autumn and early winter are the time of mole hills.
Now, these are forest moles who won’t be doing anything to anyone’s lawn, but over the next few months, there will be a lot of these little earthworks popping up.
Natural History 
We’ve got mole hills all summer long and in the fall–its like walking on a spongy mattress.
Of course here on this British offshore island we only have one species of mole which made it back after the ice melted 10,000 yrs ago and before meltwater filled the valley between here and France which became the English Channel. Legend has it that an English king was killed when his horse got its hoof caught in a mole hill. But of course we mostly only see them today on cleverly made wildlife films, except they used to be trapped in huge numbers by molecatchers back in the day. My late mother’s pride and joy was a full length moleskin coat which she wore at every suitable occasion, notably at funerals and Christmas.