Squealing noise on cold start?

[Rampage57]

We had rain the past few days in Texas, gets humid too. I started my truck and it sounded like my belt was squealing, but it stops after it warms up, well I took the chance and decided to replace the Idler pulley, the next day after replacing it, It still started to squeal. Should I replace the belt this time around?

 

[CapeRR]

Mine was doing this last year and I replaced the belt with a Goodyear Gatorback and haven't heard a squeal since. I didn't change the pully or tensioner on mine.