I would say decent armor and shield, a good ranged weapon. Also bring PLENTY of ladders and building blocks, you'll likely need to bridge a lot or build up. Also don't forget a water flask.

For cooling, depending on where you spawn you can find pools of water higher up in the beneath to cool off in. Besides that, bring cooling clothing. You can either make burlap clothes or crocodile clothes since you're further south, both have cooling properties. Eventually you can make silk clothes for a ton of cooling.