I absolutely CANNOT run inside or out without my water. After about 10 mins, my lips start getting dry...then 5 minutes later...dry throat...the 5 mins later dry scratchy throat...and so on...and so on....until I'm choking on CHALK!!! lol!
That said, I run with my water bottle in my hand. I think of it as a 1 lb weight and alternate hands every now and again. The only down side is that the longer I run, the more heat my body builds...the more heat, the hotter the water is...the last chug is usually warm!