I never take chances with my D3s. I use a thin plastic bag (found in the vegetable section of the grocery store) to cover the camera and lens. I use tape if I have to. Cheap and effective. Here in Houston where the rain comes unexpectedly, I keep a few bags in the trunk just as I always keep a bottle of deet there as well.
My Lowepro slingbag has a hood built-in. Not too sure how weather-resistant it is?
I also keep a plastic bag somewhere in the pack -- just in case. In a pinch, I also usually pack one of those flimsy plastic poncho's (the $0.50 one-time-use variety). I try to stay mindful that electronics in plastic bags might mean condensation, so it's always a very temporary thing, followed by a good inspection and drying if needed. That said, I try to stay out of the rain.
Ditch the deet.
Google: "Ben's tick and insect repellent wipes".
(The above was a joke - I'm aware Ben's has deet too.)
I'm a sucker for wipes. I absolutely love 'em. (Probably TMI, there??!)
My camera bag is pretty much always stocked with a few Wet Ones (antibacterial hand wipes - BTW, the "Fresh Scent" is fantastic!), a couple packs of Ben's, and maybe a few Nikon lens wipes.
What I like about all these produces it that they are all available in indivually wrapped foil packs, so no worries about leaks in the camera bag. Plus, they pretty much last forever until you open them.
Prior to using Ben's insect repellent, I had been using "Off", which was also available in individual foil packs. Unfortunately, whichever local store I was getting them from stopped carrying them (WalMart?), or they quit making them, so I ended up getting the Ben's equivalent online. Both work well. And cheap insurance for people like me who seem to be perfect "mosquito-magnets".
Maybe someone should start a separate thread about the strange "things" people keep in their camera bags. :-D