Knowing the status of the weather to a pilot is very important. First, it helps him plan for his flight plan. Before pilots fly they can avail of flight briefing from a Flight Service Station (or related unit that regulates air traffic) personnel. That way, he could plan ahead for his choices in case he could not make it to his destination, or some adverse weather conditions would divert him from his original flight plan. The amount of fuel that he has to take with him is also affected in planning for an alternate airport. Most of the time, it's most prudent to just wait until the weather clears before a flight is done and if it's really unlikely that the weather will improve, just cancel the flight for another day.
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