The controls and options for radar views are as follows:
Full Screen Mode:
Tap to view the map in full-screen mode without the bottom toolbars. In full-screen mode, you can pinch to zoom in/out on the map.
Tap to access the Layers settings:
Base Layer: Select from Terrain or Satellite view
Weather Layer: View Radar (U.S. only) or Clouds
Weather Layer Opacity: Slide to make the radar or cloud layer less (left) or more (right) opaque
Severe Weather Layer: Select a radio button to view the associated severe weather layer on the map
Map Marker: Uncheck this box to remove the map pin from the map
Tap to pause/start the radar loop.
Zoom in/out on the map (or pinch to zoom in full-screen mode).