storing wheels

Storing dry is generally a good idea, but as Rod Marton said above, aluminium forms a passive layer on its surface, which is very protective. Anodising is used as a surface treatment and is effectively just an artificially thickened passive layer.

The passive layer can be punctured by chloride ions from road salt and you can get small holes called pits, which are more cosmetic rather than structural but still best avoided. Therefore it is best to wash and dry your wheels before putting them away.

I would suggest to remove tyres, tubes and tape and hang them with the valve hole at the bottom. This is to allow water to drain. I've experienced corrosion (e.g. from the steel bead-wire) after seasonal storage due to trapped "water" after the autumn rains. So this is how I treat my spare wheels nowadays. It also allows you to have a good look at the hidden parts of the rim to check for any issues. I know it might be a bit much, but if you have time and you are concerned then it could be for you!

Road filth, especially winter road filth is our enemy.   I have seen 3 bar ali plate, used as a bottom of a storage box on an artic truck eaten through.  You can walk on that stuff, 5mm thick?  The alloy beads that make up my Nokon cables have rotted, some almost turned to powder.  (Next time oil, lots, when assembling and a good wipe regular).  A good wash before storage, perhaps.

Aluminium is a reactive metal, and bare aluminium reacts rapidly in air to form aluminium oxide. However the aluminium oxide forms a thin layer bonded strongly to the surface of the metal and prevents further oxidation (unlike rust, which flakes from the surface of steel exposing more bare metal).

So storing outside shouldn't be a problem. The main problem is with steel parts like bearings - but with quality wheels these should be well sealed. If not, make sure they have plenty of grease to avoid water ingress.