Darn, that's right, I forgot he was going in May. You are absolutely correct on the climate issue - I did that trip in mid-November, and while it was bearable (I would estimate in the 80-85 F range most days) I still felt hot. I'm used to wearing shorts and a t-shirt here in the States when the mercury is that high - the long sleeves and long pants thing was a bit rough!

Given the need to escape the heat at that time of year, my vote would change to a place I've never been but really, really want to visit: Sikkim. It's way off the beaten path, requires a special visa, hard to get to, and probably expensive to boot, but I will find a way there someday!

Or for something more simple, yeah, stick to the earlier suggestion to fly to Delhi and head up into the hills... But Rajasthan is pure desert, and I can imagine you'd roast there in May.