Fire and ice are the two elements of creation in the mythology, therefore both are extremely dominant in all aspects of the culture, including the futhark. Interestingly enough, fire and ice are very abundant in space. So the idea is scientifically supported. Also, if you look at how our earth is believed to be formed, volcanic eruptions formed land, and melting ice caps became the oceans. So perhaps fire and ice really did come first.
Many runes can be associated with elements. But focusing on element correspondence alone will lead you into trouble. If I were to choose one rune which stood out as fiery in the form of the same fire we light a candle with or cook over, I would pick kenaz. Sowulo would be more in line with Muspelheim's fire. And Fehu...I've never understood where the correspondence to fire came from with that one. One author must have written it and it was copied blindly. I've never seen anything in the original literature that hints to a fire association with fehu.