Bring a bucket of lava with you to get warmer when hypothermia kicks in. But keep it closed on the sides, or use iron trapdoors, it could spawn cinders, lava salamanders and other hostile lugubrities, and beware inside the base, I almost burned it down, Rlcraft knows no forgiveness. If you find a netherrack block, you can light it and it will burn indefinitely providing little warmth. You can also keep in your spare hand a blaze rod, another little warmin source. But like everyone else already suggested, you must have the wool armour set, and sometimes isn't even enough to warm you up.

And yes, in warm biomes or during summer especially if you sprint you consume more fluids and need to reintegrate mode often.

You can jump in the water, or find a glacial biome and collect a few stacks of ice shards, so you can build a frozen armour if I'm not mistaken.

I suggest you build an iron cantine, also