Hey!
I am not sure to understand the concept. Basically I should try to avoid everything since both hot/cold are slowing me down?
You are meant to use hot and cold areas to your advantage :)
Your vehicle hits top speed at 0°. If you're above that temperature, you should head towards cold areas to cool down and get closer to that top speed. And inversely, if you're under 0°, you should focus on hot areas.
It's up to you to balance your vehicle's temperature using hot and cold areas so that it remains as close to 0° as possible :)