Fixes "floor is lava" covering everything (#40743)

code/datums/weather/weather.dm

@@ -28,6 +28,7 @@
 	var/impacted_z_levels // The list of z-levels that this weather is actively affecting
 
 	var/overlay_layer = AREA_LAYER //Since it's above everything else, this is the layer used by default. TURF_LAYER is below mobs and walls if you need to use that.
+	var/overlay_plane = BLACKNESS_PLANE
 	var/aesthetic = FALSE //If the weather has no purpose other than looks
 	var/immunity_type = "storm" //Used by mobs to prevent them from being affected by the weather
 
@@ -121,6 +122,7 @@
 	for(var/V in impacted_areas)
 		var/area/N = V
 		N.layer = overlay_layer
+		N.plane = overlay_plane
 		N.icon = 'icons/effects/weather_effects.dmi'
 		N.color = weather_color
 		switch(stage)
@@ -134,5 +136,6 @@
 				N.color = null
 				N.icon_state = ""
 				N.icon = 'icons/turf/areas.dmi'
-				N.layer = AREA_LAYER //Just default back to normal area stuff since I assume setting a var is faster than initial
+				N.layer = initial(N.layer)
+				N.plane = initial(N.plane)
 				N.set_opacity(FALSE)

code/datums/weather/weather_types/floor_is_lava.dm

@@ -19,6 +19,7 @@
 	target_trait = ZTRAIT_STATION
 
 	overlay_layer = ABOVE_OPEN_TURF_LAYER //Covers floors only
+	overlay_plane = FLOOR_PLANE
 	immunity_type = "lava"