Only the last digit of the IP code refers to water resistance. IPx7 allows you to submerge the device in 1m of fresh water for half an hour, which IMO is a little excessive for a handheld computer. IPx3-IPx4 should make it pretty much rain-proof, but would probably need something done about the SD slots.
On the subject of the first number, that refers to the ingress of solid objects. If I'm reading it right, anything above IP2x would stop us having hacker-friendly accessible screws, the previously mentioned SD slots, and might even have something to say about the headphone socket, I dunno.
All that said, my Pandora got rained on today on the front edge (with both SD slots and the headphone port occupied) for about five minutes and it carried on rocking. That might make it theoretically IP23-compliant in those circumstances.