What does an auxiliary plate (dopunska tabla) with the symbol of rain and a cloud beneath a speed limit sign indicate?

1. The posted speed limit applies only when the road surface is wet or raining (Važi u slučaju kiše/mokrog kolovoza)
2. Motorcycles are completely banned during rainy weather
3. The speed limit increases by 20 km/h during rain
4. Vehicles must stop immediately until rainfall ceases