Electrolytes may help if plain water doesn’t. It’s easy to sweat out minerals when you are in the heat a lot. Plain water doesn’t replace those minerals. And eating some watermelon with some salt on it might help you as well. I find that my sodium levels get too low when I am working out in the heat and have to take more of it.

Also take a shower to help you cool down quicker.

Being outside, sweating, and then drinking loads of water can actually put your electrolytes out of balance, which can result in a headache. It dilutes the sodium, etc, you have left in your body. Try drinking a gatorade or adding an electrolyte power to your water bottle. It might help.

I'm on meds for headaches but the heat will definitely make my head pound. All I can do is go back inside & cool down.

Can't help you. I've not had a headache in decades (and for a good deal of that time I was hungover too many times).

I woke up with one today. I knocked back four extra strength Excedrin and came here to similar worlds. Feeling better now.

Try a cool bath/shower... as close to cold as you can bear it - also check out the symptoms for heatstroke, because it sounds like you might be getting a mild case of that if it's not dehydration.

Could you have actually overdone it with too much water.

any better?

put an ice pack on it.....

Stay inside with the air conditioner on cool

Turn on the AC and stay indoors.

salt, you sweat it out, and drink a lot of water so you need minerals