go to weatherunderground.com type in your zip or town, st in the top left search location. it will pull up your local forcast. now scroll down the page and you will see a link in blue on the left side of the page. the link says "september calendar view" double click this and it will show you the daily and monthly totals. you can also go to previous months and years to check past data.
thats what i do. it will also show you monthly averages to compare against actual