ue-udw-spatial-weather

Use a Weather Override Volume from Ultra Dynamic Weather. Its spline component defines an arbitrary region shape, and you assign it a weather preset, transition width, and priority so the area blends from outside to inside weather as the player crosses the boundary.

Use a Radial Storm actor, which renders local cloud coverage, fog, and obscured lightning visible from outside. Distant-storm visuals require Sky Mode set to Volumetric Clouds; with other sky modes it still affects weather state but shows no visible storm.

Add a Weather Mask Brush for simple shapes or painted textures, or a Weather Mask Projection Box that captures meshes like roofs and masks effects beneath them. Both draw into a render target sampled by the weather material functions.

The Transition Width setting is too small; the default is kept small to keep the actor compact. Increase it substantially so the player crosses a smooth spatial gradient between outside and inside weather.

Yes. Call Move Storm Over Time on the Radial Storm actor with a target position and duration, optionally fading out and destroying the actor at the end. Combine with Fade In Storm after spawning for a full lifecycle.

Check the Control Point Location Source setting on UDW, which determines what location is tested against volumes. It defaults to Player Pawn; if set to a manual vector that does not track the player, the volume will never trigger.