There聮s an easy fix, a medium fix, and a more complicated fix. The easy fix is to pack a half-dozen white kitchen garbage bags with your luggage. Stuff one down inside your daypack, and anything that needs to stay dry goes inside. I suggest taking several as it聮s not that hard to puncture them. But they聮re light and waterproof and cheap. What聮s not to like? Your pack might get wet, but it will dry out overnight.
REI’s 20-liter Duck’s Back Cover

I like it better than the medium fix, which is a pack cover. REI聮s 20-liter Duck聮s Back Cover ($18; rei.com) is made from taped polyurethane and is totally waterproof. But now you have to fit the cover to the pack, then take it off when you want to retrieve something. With the garbage bag liner, everything is right there. Still, pack covers work well. They do keep your pack dry, which could be useful if it is really, truly pouring. And it can do so there, even in July.
Complicated fix: Buy a waterproof pack. Vaude聮s Aracanda 30 ($110; vaude.com) has sealed seams and waterproof material, so it will keep your gear dry almost regardless of conditions. But, now you聮re buying a new pack. Arc聮teryx Naos 45 (arcteryx.com) offers more carrying capacity (probably too much, nearly 2,700 cubic inches) and a more sophisticated design, but it will set you back at least $380 depending on where you buy it.
So, assuming you already have a pack you like, I聮d get the garbage bags.
The Gear Guy reports from , the bi-annual gearapalooza in Salt Lake City. Check out his top picks for gear to watch in 2007.