In this hot weather a really quick and easy way to check your horse’s hydration level is to pinch their skin. If when you let go it immediately springs back to normal then hydration levels are fine, if though the skin retains a pinched shape for a short amount of time or slowly reverts it is a strong indication that your horse is dehydrated.
This video illustrates how the skin will spring back on a healthy hydrated horse.

that is one healthy hydrated and good looking horse 😉
There has been a study to show that skin tent check is not
really an accurate measure of dehydration.
http://www.ncbi.nlm.nih.gov/pubmed/18356129
http://www.horsetalk.co.nz/news/2008/12/030.shtml#axzz2ZJqJMEA0 I
think the conclusion is the best thing to do is to offer water ad
lib. 🙂 Which is what we all do anyway!
Interesting thanks for the article. I have been taught through PC exams through the years (up to A test!) that it was accurate so very interesting to know otherwise.
Agree though constant access to fresh water plus added electrolytes in this hot weather is the most sensible course of action to ensure your horse stays hydrated.