When its warm outside, I have no problems whatsoever.

Now that its a cooler (below 50 degrees) I'm having issues. When I put my key into the ignitition, it won't turn, almost as though my steering is locked. Doesn't matter how I jiggle or move the key around, it will not turn.

This happened last year during winter as well. Over the spring/summer, this issue went away.

Car: 1990 Civic EX, 5spd.

 

hows the key look? Is it worn out?

My friend had this problem with a new car...but it was an outside lock.

 

Well, the key is a bit old (or so it seems)... I never did get the original when I bought the car.

Could this be the reason why? Would key-making stores be able to replicate a key using the one I have, which is also a duplicate?

 

Yes - have a new key made and go from there - it's a possibility that your key is just too worn.