Conditions

Name	Effect	Maps	Opens at	XP bonus
Storm dusk		Every map	From the start
Night		Beach, Village, Swamp	Threat III	+10%
Fog	x2 Fog -20% Light	Beach, Village, Swamp	Threat IV	+10%
Blackout	-75% Lamp Light	Bunker, Sewer	Threat IV	+15%
Rain	x1.35 Fog	Beach, Village, Swamp	Threat I

Pictures

NightNight on the open maps: a cold moon and the dead wading in.

FogFog rolls in off the water and hides what's coming.

BlackoutUnderground, the lamps fail and the halls run on emergency red.