Hyperthermia is a character effect in DayZ Standalone. Hyperthermia is caused by the body temperature getting to high, usually due to being near a fire to long or holding to many hot items. When your termometer icon in the bottom right turn red or flashing red you are suffering from hyperthermia
It is suggested that you dont sit next to a fire for to long. If you are cooking meat or the like and you carry to many of these freshly heated items your temperature will rapidly rise, to prevent this you can carry all your hot items in a container or clothing item in your hands until the items have cooled of. If you are suffering from hypothermia you can decrease your temperature by standing in a windy area or if necessary getting yourself wet.
Once suffering from Hyperthermia you will continuesly lose health aswell as water faster. This can lead to dehydration or death.