1:17 p.m. on April 6, 2011 (EDT)
nworbled,
Sorry I didn't notice this earlier. You can get some clues from my trip report on Kilimanjaro here on Trailspace. I did the hike in December, which is at the tail end of one of the rainy seasons.
Most (all?) of the posts above seem to be from people who haven't done the hike. Make no mistake, almost all the routes are hikes, not climbs, on quite good trails.
During the first day from the gate, you will be in rain forest, and same on the last day back to the gate (and probably on the next to last day as well). You may want a full rain suit (jacket and pants), although this is one of the very few places I would ever recommend a poncho (a good quality poncho with snaps on the sides, meaning a nylon poncho, not one of the cheap plastic things that tears easily). If you click on the third photo in my report, you can see a large size version, and in it you notice that one person (a guide) is carrying an umbrella and another is wearing a poncho. It is hot and humid in the rain forest (remember, Kili is only 3 degrees south of the Equator). So a full waterproof jacket and pants will not breathe anywhere well enough (click on the summit photo and you will see that I have on eVent jacket and bibs - Goretex is much poorer at breathability than eVent, and in the rain forest sections, I was sweating heavily, despite having the pit zips wide open). A poncho allows enough ventilation to reduce the sweat accumulation.
I highly recommend using a Primaloft bag and a light Primaloft jacket (Integral Designs Dolomiti proved ideal on that hike). I took a good down sleeping bag because I anticipated it would be much colder than it turned out to be (I had no problem with getting the down wet because (1) I have many years experience in camping in wet conditions and know how to keep down dry and (2) I stored everything each day in a Sea to Summit drybag that was to be carried by the porters - you are required by Tanzanian law and park regulations to use local porters, guide, and cook on Kili).
Definitely use layers that are easy to get on and off. You won't need long johns until the upper part of the mountain. You didn't say which route, but if you are coming from the more usual trails, that would be from the Shira (12,000 ft) or Barranca (13,000 ft) camp or equivalent on up. I wore Supplex (by REI or Columbia, don't remember which) pants and an Ex Officio light shirt most of the way, with a fleece jack at the lower camps and used the Dolomiti higher up at Barafu (the highest camp). I did wear the fleece on summit day from Barafu to the summit and back down to Barafu, but took it off for the hike back down to the gate. I also wore my Wild Things eVent jacket on most of most days, until part way down from Barafu.
Weather was - day 1 - pouring rain in the rain forest, which let up as we got to Machame (first camp), day 2 - intermittent rain turning to sleet most of the way to Shira (second camp), day 3 - rain/sleet/dense fog on the way to Barranca camp (we skipped the Lava Tower, which most people do because it is a useful climb and descent for acclimatization, but with the fog so thick at the trail junction - about 10 ft visibility, and my acclimatizing easily, there was no point in taking that side trip- folks who did go that way said visibility was low enough that they could barely see each other at arms length). Day 4 - light rain plus snow on the way to Barafu. Day 5 Christmas Eve day - clear, but wore the Wild Things eVent as a wind breaker to the summit and back to Barafu, then part way on down to Mweka camp. Day 6 - dressed lightly for the last few kilometers back to Mweka gate - hot and humid.
One bit of advice - you will need to take an antimalarial of some type. I would advise not using Doxycycline, rather using one of the others. My reasoning is one of the side effects - Doxy increases your sun sensitivity (I burned my nose badly on the sunny summit day, despite liberally coating with SPF80 sunblock with lots of renewals). I strongly urge reading the side effects of your medications very carefully several times. The reason we had settled on Doxy was that you take it daily for a week or so before the trip and 4 weeks after, vs a couple of the others that are once a week. We thought that the daily dose would be easier to remember. I have talked to others who chose Doxy and got the same response - choose one of the others. But do read the side effects, because one of the others has potentially worse side effects. OTOH I know one person who says he won't take any antimalarial, feeling it is just easier to deal with the periodic recurrences than to down medicines before actually needed - your choice, just read carefully and talk to your medic.
Oh, yeah, it was far from dusty. In fact, it was mostly muddy or rocky, except for the scree slope that passes for a trail the last km or so to the crater rim.