The heat and water issues are good ones to bring up, too. On our first night we camped above the redwall, so most of us were carrying nearly 8 liters of water to start off with. The Colorado and Hance creek were our water sources during the trip, although you can stop at Page/Miner's spring on the way up to Horseshoe Mesa. I don't think I ever started a day carrying less than 4 liters of water. Our weather was pretty good, but in April the afternoon highs were probably at least high 80s, and it's true there are some good stretches of trail with little shade. We typically made it to camp at 3-4 in the afternoon and spent the rest of the afternoon rehydrating and finding whatever ways to cool off that we could. We were fortunate in that the Colorado was running clear as it ever does while we were there. It can be very muddy, which makes getting water more difficult as you pretty much have to let the silt settle out of the water before further purifying it for drinking. And after getting to camp I typically made about 6 liters of water and sometimes had to re-supply in the morning before starting hiking. The only cold weather we encountered was in about the last hour of hiking out, where a storm came through and dropped some very cold rain and sleet.