Actually, here's the deal.

THC (what gets you stoned) is not water soluble at all. Thats why drinking plain water a lot doesn't help you on drug tests. Though, it is fat soluble, and oil soluble. So, that means when cooking with it, you need to make sure there is some fat/oil in there (and in tea that means milk). Plus, it must be at high temperatures to extract the THC, and you don't wanna eat anything at least 2 hours before you try consuming the weed.

So, it is possible to make weed tea, just make sure you add milk along with it. Make sure it stays warm too.