Well, the Storm Lord (complete divine) is weather-focused, but it's weaker than pure Druid. From a mechanical perspective, you pretty much want to stay Druid.
Now, for feats, you might consider the reserve feats from Complete Mage - Born Aloft, Clap of Thunder, Hurricane Breath, Storm Bolt, Wind-guided arrows, and Winter's Blast are all flavorful choices that match what you're after, even if they're not mechanically the best choices (but then, as a Druid, you've really only got one must-have feat, and that's Natural Spell).
Edit:
You might also consider Contemplative - a one level dip could net you the Storm domain, Weather domain, or some such. There are also some domain staffs, although I can't remember where to find them at the moment, that let you convert one spell of each level per day to the specified domain.
Edit 2: Ah, Domain Staffs, Complete Champion, 36k each (18k materials, 1,440 xp to craft); page 143 is the one you want to look at. Requires Craft Staff, and access to all 9 spells in the domain. You can only be attuned to one at a time.