Vibration in the rain

I have just purchased a 2000 4Runner and love it... my only complaint would be that i have noticed a Vibration.. and its only when i go over 60mph and in the rain... dry roads.. no vibration... anybody having a similar problem??? the front grille bumber, the tires? rotors vibration?

It might be the tires. When I had low tread on 1 of my tires, my car started to vibrate, especially in the rain. I think its because; if the tread is to low, it can't move the water from inbetween the road and away from the tire.