Late night can be taken to occur from about 2 am to sunrise. This is the time of the day that typically the low temperature will occur. The low temperature often occurs around sunrise. Typically the temperature will cool hour by hour during the night time hours and reach a minimum around dawn. This is the traditional time of the day that the low temperature occurs. If the low does not occur around this time it is known as a “non-traditional” time for a low temperature. This can happen for example when a front comes through and causes the low temperature to occur at a different time of the day. The wind tends to be lightest at this time of night since the air is typically stable. Sunrise is often accompanied with light or calm winds, no precipitation and a high relative humidity. With high humidity, low clouds can be quite common around sunrise. With stable conditions, thunderstorms are much less likely during the late night than in other times of the day. Exceptions can occur such as when a front moves through during the late night hours. This can contribute to stronger wind and storms. The weather tends to not be too threatening during this part of the day and most people tend to be asleep during this time. Thus, it is a time that it is dark and the least amount of people will be observing the weather. It is typically a quiet time of the day weatherwise. The late night is the most common time of the day that dew or frost develop. Dew forms when the temperature drops to the dewpoint and the relative humidity reaches 100%. Continued cooling will cause moisture to condense out of the air. If the dewpoint is below freezing then it is known as a frost point. When the temperature drops to the frost point then frost will develop from moisture going from the vapor state to the frozen state. In some situations the temperature can cool to a dewpoint that is above freezing and then continued overnight cooling causes the temperature to drop below freezing. In this situation dew will become frozen and there can be both frozen dew and frost that is observed. |