MR2 startup loud sqealing sounds

Hey guys, my 1991 MR2 makes a loud squealing sound when I start up my car. Its sooo loud it'll wake up the entire neighborhood:banghead:. When it rains, the sound gets even worse or when I turn on my headlights the sound will come on when I stop at a stop light and go away when I rev my engine high. Is it a belt or a battery problem??, cause when the sound comes on the dashboard lights will dim.

Its your accessory belt slipping, try tightening your tensioner which is located low on the passenger side of the engine bay. You should not be able to push the belt down more than a 1/4 to 1/2 inch. You can also spray some belt conditioner on the belt in addition to tightening it. Good Luck!
S.B.