Up here the early fall is the best time. It's to cold for weeds to grow and the ground tends to hold moisture longer. The problem I have now is with bent grass taking over my lawn. I'm told there is nothing I can do about it and that pisses me off.
The birds eat the seed around here. So I try to toss it out when we have the first snow of the year, that keeps the birds from getting it and the melting snow helps get it in contact with the soil.