1997 Infiniti I30 Noisy belt

I've noticed in the extreme seasons (winter and summer) whenever I start my car the belt makes a loud whistling noise. After warming up the car for a few minutes it will go away but then as soon as I start driving and brake, the noise starts again. It's consistent with making this noise on very cold days, rainy days, and when it's hot outside. It's been doing this on and off for about 3 years. I've been told if it's not fixed, it could break the engine. I went to have it looked at about a year ago and the mechanic said he replaced a belt but when I got the car back the noises started right up again. Not sure if the belt needs replaced or it now needs to be tightened. Any advice you can offer would be greatly appreciated. Thanks.