Mac Air 13" (2015) warmer than before

Hello there

I just have a simple question - I've recently noticed that after installing High Sierra (10.13.1) my Air started to get a little warmer (and sometimes actually warmer) even when I just browse the web (I use Firefox and Safari) or watching a Twitch stream.

Is it normal with the new iOS or I'm I actually doing something wrong (or something is not right). Mac Air is early 2015 with 8GB and 128 SSD (around 40GB still free) and I scan it regularly with Malwarebytes.

Thanks a lot!