Never wear them - most uncomfortable item of clothing ever invented.  

In summer I wear lighter trouser suits, usually in linen.  If I wear a skirt I make sure it's a long one, that way I can apply some fake tan to my legs.  Surely you can get away with wearing trouser suits or at least some fake tan with a knee-length or ankle-length skirt??

Personally I stop wearing any tights/socks from about April/May to early Sept.

Having said that I would always dress for an interview and would def wear tights then.

What is your company policy on dress code?

G