A basic speed law says that you must travel at a speed that is consistent with existing driving conditions. These include weather, traffic, and road conditions.
Or put in other words: No person shall drive a vehicle on a highway at a speed greater than is reasonable and prudent under the conditions.
Such a basic speed law is used in all 50 states.
Remember, it does not always matter what the speed limit sign says.
In bad weather, you must reduce speed. If there are potential hazards on the road, you must also drive slower than the posted speed limit.