Situation: a human mage with no vision enhancement is onboard a ship. It's in the middle of the night and raining heavily. GM applies a -4 modifier to all actions due to the darkness and bad weather. Does it apply to summong too?

Vision, no.

Bad weather, I'd say yes if it is physically disruptive (mist no, gale yes).

I would say "No", since you don't need LOS or even sight in general to summon a spirit.

Just don't try to summon a spirit of fire under these conditions

-CJ

The mage had a bound spirit of fire which he unleashed on the enemies. Didn't last long.

I would also not count vision modifiers, unless they are actually distracting.

You should be able to summon with closed eyes.

Bye
Thanee

What he said

I'd ask the GM to break out what each part of the -4 is actually from. Rain, rolling of the ship in the water, those I could see affecting everything involving some kind of action, including summoning.

Even if it would apply, the mage could still project and summon the spirit from the astral plane.

... and vision modifiers shouldn't, though being tossed around in a stateroom at sea could...


Exactly.

Replace 'could' with 'would be required to'.