Is your sound breathy? You might be sending too much air in your voice. If you feel your voice at the front of your larynx, that means you are sending too much air pressure forward there and not allowing the back of your throat to relax open. When that happens, the front of your larynx is pulling the vocal cords as opposed to the back. This creates a misalignment that is not so comfortable for your vocal cords and could be irritating. Which also explain the dehydration as your body is trying to compensate. Start by using less volume during your exercises and concentrate on guiding your resonance up and down along your jaw line and behind your ears.

Valerie

By thirst do you mean your internal "ahh I feel satisfied now" thirst or your "my mouth and throat are nice and moist now" thirst? If it's your internal - there's something else going on. Excessive thirst CAN be a sign of a thyroid issue - which, since the thyroid resides in your throat can cause vocal issues (a swelled thyroid can limit your larynx and vocal production)
Be careful not to drink TOO much water- there is such a thing as water intoxication, it takes A LOT of water, but if you're chugging to satiate your thirst you could be at risk. Be on the lookout for rapid, unexplained weight gain, nausea, confusion and vomiting as these are signs of water intoxication - which can be fatal.

Nerves - nerves can give you dry mouth. Are you stressing about your technique and doing it right? When I get nervous my mouth gets dry, my ears block, it can create quite an issue - just chillax, no one is judging you. Warm-ups are about discovery. You'll also never find the "proper" feel until you relax! I know sometimes using the keyboard/pitch finder for my sirens can make me feel a little stressed and intimidated. I start cracking, my breathing jacks up and It's not the note, it's my brain! I step back and take a minute. Go back to basics and just walk around my practice room straightening up or reading some unimportant article doing sirens at my own pitch and pace. This lets me reset and relax so I can get back to isolation work in the right "place" mentally and vocally.

In any event - don't forget the IMPORTANCE of the "misting bottle" full of distilled water. Applying the water directly to your mouth and chords works a lot better than drinking till you're bloated!!

cool ill try out the distilled water and thanks

Normally I drink 3,5- 4 liters of water on session day too, the reason is that during session which takes 2 hours or like, you breath out I guess at least 1 liter. But I don´t get thirsty at all. I drink during my session, because my throat gets dried. But if you drink a lot and you´re thirsty, there is something not OK going on, and I would get things checked out. never heard about what Diane said, but she is more experienced in that and she knows better about this issue.

Honey helps a lot too. It gives you a nice "coating" and gets the saliva glands going. It's an old remedy I have found to be true as well - it's been said that eating locally farmed honey can help combat some allergies - as the honey is made from the local pollen and it gives you body small doses to build immunities - basically the same principal as a vaccination.

If you have diabetes or any other reasons you shouldn't have sugars - this may not be the best idea.

this thing interests me too. How much honey (in a count of a tea spoon) you take when your throat gets dried?

I just keep a bottle near me. If I think I need it, I take a "sip" and just let it coat my throat. I don't know the exact amount. It's kind of like asking "how much food do you eat before you're full" - it just depends.