I added a scripted effect to the player that uses the OnHit event, which I want to trigger only when the player is physically hit by an attack (not spell, etc). So, inside the OnHit event I added the line:

if (akSource as Weapon)
; ...
endif

This seems to work fine. Enemy spells are blocked on that condition and don't trigger the effect. On the other hand, hits from enemy attacks trigger correctly. But then I noticed the condition is accepting my own Blizzard damage. In fact, every tick I stay inside the Blizzard hazard causes the script to proc.

So, I'm here considering that "if (akSource as Weapon)" is true when the damage comes from a hazard..

Is this correct?
How can I change this condition to really only allow physical attacks from enemies to pass?

Weird, I wouldn't have thought that.

What's in akAggressor when it's the blizzard?

Good question. I'll take a look at that when I got home.

But your question gave me an idea
Maybe I can try making it work only when the attacker is an actor:

if (akAggressor as Actor && akSource as Weapon)