A: I’m cold.
B: Put a sweater on.

Turn the heater on.

Put some clothes on.

Move around a little.

Drink some coffee.

Drink some hot tea.

Take a hot shower.

Make a fire (in the fireplace).

A: I’m hot.
B: Open the window.

Change into some cooler clothes.

Turn the fan on.

Turn the air conditioner on.

Take a cold shower.
Drink something cold.