At home, we get to set the temperature. This is not the case in most other places, especially in public transit settings. To make sure I’m comfortable no matter what, I bring a sweater: my go-to is a blue wool zip-up cardigan I’ve had for about a decade now. Over that time it’s kept me warm on planes and hikes, and severed as a pillow on more than one occasion in warmer weather. While it might take up some room in a bag, this is a must.