Weather is pretty boring in 5e. Rain and fog obscure, extreme temperatures cause exhaustion, and wind makes ranged weapon attacks and flying harder. woo hoo
In Out of the Abyss they gave us Faerzress which is a weird magical energy aura which felt similar to how magic works kina, but that is about as exciting as it ever got. Curse of Strahd had the plane shifting mist which brought you to Barovia which is cool. Outside of these and a few other notable points weather gets shoved to the back and generally gets ignored.
here are a few fun ways to make weather magical.
Fog of War
Make the weather aggressive and dangerous. There are plenty of reasons to find shelter when a natural cloud kill or a tornado of fire is rolling over the hills. This not only gives the adventurers reason to prepare Control Weather or Gust but it is always nice having obstacles that the heroes can’t just murderhobo through.
I love the idea of rain water pooling in weird geometric shapes in the air, fog making the shape of a battle that happened long ago, tiny droplets of light that cascade to the earth which deal radiant damage to undead, and gales of wind that cause your bones to shudder since its identical to the wail of the dying. Not every phenomena needs a clear purpose or cause, but by adding these bizarre qualities to weather you show your players that magic is living in your world.
Weather AND Combat
Want to spice you an encounter with a manticore? Mid-combat have the rain freeze to become icy daggers! Just make sure to foreshadow the weather with snow or hail. There are lots of ways to use weather to spice up an encounter that would be otherwise dull, you just have to spend a bit of time considering the possibilities. It also allows you to end a combat early if the players are getting trounced or allows a villain you want to keep alive breathing when it starts getting low on hit points.
If nothing else it allows you to play with encounters like the setting in smash brothers. (I wonder how the players would handle an encounter where everyone benefited from Barkskin and Freedom of Movement? Time for some oily rain that clings to creatures in a scaly way!)