Adverse weather driving limit, how often can you use this?

Adverse driving conditions means snow, ice, sleet, fog, or other adverse weather conditions or unusual road or traffic conditions that were not known, or could not reasonably be known, to a driver immediately prior to beginning the duty day or immediately before beginning driving after a qualifying rest break or sleeper berth period, or to a motor carrier immediately prior to dispatching the driver. Normal heavy traffic slowdowns are not considered adverse driving conditions

According to FMCSA, “If unexpected adverse driving conditions slow you down, you may drive up to 2 extra hours to complete what could have been driven in normal conditions. This means you could drive for up to 13 hours, which is 2 hours more than allowed under normal conditions. Adverse driving conditions mean things that you did not know about when you started your run, like snow, fog, or a shut-down of traffic due to a crash. Adverse driving conditions do not include situations that you should have known about, such as congested traffic during typical “rush hour” periods.

§395.1 Scope of the rules in this part.

Guidance Q&A
Question 5: How may a driver utilize the adverse driving conditions exception or the emergency conditions exception as found in §395.1(b), to preclude an hours of service violation?

Guidance: An absolute prerequisite for any such claim must be that the trip involved is one which could normally and reasonably have been completed without a violation and that the unforeseen event occurred after the driver began the trip.

Drivers who are dispatched after the motor carrier has been notified or should have known of adverse driving conditions are not eligible for the two hours additional driving time provided for under §395.1(b), adverse driving conditions. The term “in any emergency” shall not be construed as encompassing such situations as a driver’s desire to get home, shippers’ demands, market declines, shortage of drivers, or mechanical failures.