I get cold when running?

i run about 5 to 6 miles a day, 6 days a week, 15 year old girl. after about 3 miles at like a 7 or 8 minute pace, (even in the blazing sun 90 degree weather), i start to get chilled and freezing when i run and my skin even feels cold. i think its because im dehydrated, is this true? one time after i ran, i stayed cold for 4 hours after