Running
I prefer outside Running...Luckily I have a Church near me that has a ton of property and they have a lake on it, so they built a "walk around" with lights so it can be used 24hrs a day, it is a nice 1/4 jog, so I will go out and run 2 miles, meet all sorts of people who are exercising as well, and I try to increase my time and distance each week.
Treadmill is for the rainy days, I just think I get more of a work out outside and the motivation is better for me anyway.
Only problem when it is 97F and 100% humidity, I have to wait until early morning or late at night, Just can't hack that heat during the daytime, no need to go into heat stroke.