Hello, Tothetrail!!
I just returned from doing the loop you described (July 16-21, 2007.)
1. Weather: It was glorious, temperatures between low 80s during the day and 40s at night. Almost no clouds, incredible sunsets. Get out of your tent after the moon sets for spectacular stars.
2. River water levels: Not an issue. All creeks were very easy to cross. There was running water along the way each day. If you bring a water pump/filter, you will never need to carry more than a liter of water at a time.
3. Mosquitos: I think I used DEET once. The whole area is pretty dry.
4. Must-have items:
WALKING POLE/S!! You will be doing your knees a favor. I used only one. Some of my companions used two. I'm not sure there was much difference. Since I was taking photos along the way, I liked having one hand free.
SUN SCREEN. The sun is very intense, especially walking over bare rock.
FOOT CARE PRODUCTS (e.g. Moleskin). After the ten-mile walk downhill from Sunrise to Merced Lake, several of us worked up truly spectacular blisters.
CASH!! Although you can buy whatever you want at each camp with a credit card, you will also want to bring cash to tip the young people who work there. They really do rely on tips, and they do a terrific job, so I'd suggest $5 a night minimum as a way to say thanks.
5. Food: The food served at the camps was terrific. At 7 AM, tey set out hot coffee and water for tea and hot chocolate. Then breakfast at 7:30 AM. Breakfast each day was hot cereal with raisins, brown sugar and coconut, then pancakes, bacon, sausage, and eggs. Lots of coffee, tea and hot chocolate. Hot beverages are set out again at 6 PM. Dinner is at 6:30 PM. Dinner each night was plentiful and delicious. They serve the same food at each camp each night (e.g. Monday was chicken night, Tuesday was pasta, Wednesday was fish, etc.), although each cook can prepare it the way he/she wants to. For example, we had halibut baked in parchment one night, steak teriyaki another, chicken with a basil pesto sauce, etc. There were also excellent vegetables, freshly baked bread, sinful desserts. I don't think the box lunches were worth the price ($12+). You can buy an excellent, filling sandwich a la carte for $3+. The stores at each camp sell candy bars, trail mix, fruit, etc.
I'll be happy to answer any other questions you may have.
HAVE A GREAT TRIP!!!
NinaJane
NinaJane