You will get dizzy, weak, cold, among other things.
Is this your first fast?
You should really take some time while your fasting to read a lot of the threads in here about water fasting.
The reason your body will become weak, tired, dizzy, cold and everything else is because you are realing toxins that have been built up for so long. Water Fasting is very hard to do and not many people can do it without surrendering. I know I have fasting before manytimes on water and the first time was actually the easiest for me. I just went on with my day, but I felt lathargic and just aweful. I got over it though at about the end of day four.
When I started though I wanted it for weightloss and weighed about 149, now I'm at 140 but was at 130 and don't feel so good anymore so I'm doing it again.
By the way.....
Are you doing this for weight loss? If you are, you are going to be awefully skinny when you are done. If you're doing it for health puposes, then more power to ya'. :)
Just be careful and please check with a Dr. first, someone needs to supervise you for such a long fast, especially on water.

Anyways, I hope I've helped you at least a little bit.
I'm sure verteran fasters will come in and add to this as well.
Take care and happy fasting!!!!!
Ivana ;)