I'll be out in the Chatham / Orleans area of the Cape in mid-August, just wondering if any New England experts could give me some advice on traffic.

I will probably be taking an international flight from Logan on a Sunday night around 7pm and would need to drop off a rental car. Based on your experiences with traffic returning from the Cape, how early should I leave Chatham to make it to Logan in time? Google maps says its 1hr 38m to to Logan, but can't imagine this will be accurate on a Sunday in the summer.

Thanks!