Not necessarily..if the weather causes a safety issue he can't make them workThis might seem harsh but as the employer he has the right to send them out in any weather as long as they are contracted to do so. If they decline to work they they would be liable to face disciplinary action.
Also he should be paying them regardless of what gets cleaned at what doesnt, weather delays are customer cancellations are not the employees problem. All the employee has to do is go out and do his job.