Ryan Seacrest is pulling back the curtain on “Dick Clark’s New Year’s Rockin’ Eve” … revealing it’s a longer day than many realize — and, he needs some pain relief to weather the storm.

The talk and game show host stopped by “TMZ Live” Tuesday while walking around Times Square before the night’s festivities kick off … saying it looks beautiful in NYC right now — but, it’s expected to start pouring when they get on the air.

While the show doesn’t start until 8 PM ET, Ryan’s already preparing for the show … explaining the production is in dress rehearsal mode — and, as performers do a dry run of their shows, Ryan and the rest of the crew will run what they can too.

We also talked to Ryan about the bathroom problem — there aren’t ever enough for everyone who packs the area. Seacrest says he’s heard people wear diapers … though he swears he hasn’t directly asked anyone.

Ryan says he’s most excited to see all the performers … specifically naming Carrie Underwood and the Jonas Brothers. He also marvels at how quickly the event staff is able to clean the whole area up.

Seacrest himself won’t be involved in the cleaning … ’cause he says he’ll need a seat and a whole bunch of food to eat — though his options after midnight on New Year’s Day are going to be somewhat limited, even in The City That Never Sleeps.

BTW … celebs are set to pack the stage for the show tonight — with Lenny Kravitz, Mark Ambor, Mickey Guyton, Megan Moroney, Sophie Ellis-Bextor and TLC joining Underwood and the Jonas Brothers in providing the entertainment.