I'd say it's too early, but if the weather is warm where you are he could play in the garden with no nappy and a potty to hand, you can see if he can feel the need and do it on the potty. If he just wees and didn't know it was about to happen, I guess he's not there yet.
Seeing himself weeing with no nappy to hide it should help him identify the feeling just before he wees and try to get to the potty.
Well in the space of an hour he did 4/5 wees! That's a lot isn't it?! He does drink A LOT but he doesn't seem to be holding much in. He was also getting upset about not having a nappy and wouldn't go in the garden (so much less clearing up!) as it's too hot.