So I'm one of those people who enjoys games like minecraft being a bit more challenging and I was thinking "without having to constantly rebuild my world, what would be a fun way to do that?" my thought was, what if air had a heat value and you could die from heat exhaustion or hypothermia? Basically fires and lava would give off heat, stone would consume a little bit and ice a lot (that's not quite right for igloos to work), and it basically just spread it's value to the spaces around it. Therefore you could run a fireplace in your house in the middle of the snow/ winter and your house would be warm while the outside gets deadly cold. This would also result in low caves being a bit cold (as they are in reality) because the stone would consume a tiny bit of heat the farther down you went. Would this extra processing melt a server? What do you think of the idea? Let me know!
Edit: This would also include stoves (AKA furnaces) in the building, etc, and seasons would dictate the amount of "heat" lost to the ceiling of the chunk or gained from it.