Fall Into Autumn Swap Topic

Here is the question and answer to the weekly topic for the Fall into Autumn Swap.

Now that in some geographic locations the weather is starting to turn cooler, do you change the type of yarn(s) you knit/crochet with?
If so, what do you now knit/crochet with instead and why? If not, why do you not switch and what do you knit/crochet with?

When the weather starts cooling off, I tend to put away the lighter cottons and go more towards wools and alpaca. That being said, I still knit with cotton year round when I am making dishcloths or sample swatches. It allows me to see my stitch definition and see where I am making mistakes. I'm really not picky. Yarn is like chocolate--I've yet to find one I don't like!