Could you suddenly suffer ftom heat exaustion if you have kept hydrated and have been out of the heat for 2 days?

Yes : If you only hydrated with water then you are replacing the volume but diluting your electrolytes like your sodium and potassium . If your NA IS LOW YOU WILL FEEL HEADACHE THEN CONFUSION THEN POSSIBLE COMA.if your K is low will start with muscle ache to cramps to weakness to severe weakness . Replace your loss with Gatorade or you can even take some salt tablet to help replace your lELECTROLYTES

Heat exhaustion: Heat exhaustion is caused by a loss of salt and water from the body, usually through excessive sweating.Help the person to a cool place. Get them to lie down with their legs raised. Give them plenty of water. Follow if possible with a weak salt solution - one teaspoon of salt per litre of water; assist the person to drink it. http://patient.info/health/dealing-with-the-effects-of-heat