Although this part of the continent was not very south and was very close to Hin, the difference in temperature was a lot. It might have been because of some thaid, or because of some natural phenomenon, but Erik had no way to know.
Even though Erik knew he could beat the Thaid, he decided not to fight it. It was a smart choice—they had only just arrived in Mur, and starting a fight now would be pointless.
Erik needed to focus on more pressing matters—finding his friends, securing food and water. The Thaid could wait; their survival needs came first. Besides, unnecessary combat would only drain his energy and draw unwanted attention from other creatures lurking in the forest.