No matter what time of the year you go, it's likely to be extremely hot. In order to avoid heat stroke, make sure to bring tons of water with you and possibly a hat to keep the sun off your face. It's also smart to just take your time. Go slow, sit down, and rest every so often so you're not pushing yourself too hard in the environment. And whatever you do, make sure not to drink from any water bottles with a broken seal. Vendors are known to save money by reusing bottles and filling them with tap water, which most Western tourists are not used to and proceed to fall ill from. One trick to make you think you're safe is putting plastic over the cap to make an old bottle appear new. I ended up sick for over a week because of it. It will ruin your trip if you're ducking into the bathroom at all times, so learn from my mistake.