|RECORD TEMPERATURES AND TIME OF DAY
METEOROLOGIST JEFF HABY
One piece of information that is often included with the daily almanac is the record temperature extremes for the day. The most
typical extremes to run into are the record high temperature and the record low temperature. Record high and low temperatures
typically occur at a time of the day they are expected but there are exceptions.
A record high temperature tends to occur in the afternoon hours. This is not too surprising since this time of the day in general has
the warmest temperatures. There is an exception to this that is worth mentioning. An event called a “heat burst” can occur and produce
extreme warm temperatures even at night. This event occurs when relatively warm air aloft is forced to the ground. The sinking of
the air causes it to warm further by the dry adiabatic lapse rate. Temperatures can sky rocket to over 100 F even at night. Although
fairly rare, these events have been documented and they can lead to record highs occurring at untraditional times of the day.
A record low temperature tends to occur late at night just before and around sunrise. This is also not too surprising since this time
of the day has the coldest temperatures in general. During an exceptional cold spell, a double record low can occur just a second
apart. This happens when it is just before midnight and a record low occurs and then at or just after midnight a record low occurs
for the next day. Thus, one cold weather event can produce multiple days of a record low.
A record high temperature and a record low temperature are particularly impressive when they occur at an unexpected time of the day
such as a record low occurring during the afternoon or a record high occurring at night. It takes exceptionally cold or warm weather
and fast changing weather for this to happen. One situation this could occur for a record low temperature is when a very strong
cold front moves very far to the south and the temperature drops to record lows after frontal passage during the daylight hours
at a location that typically has tropical like weather.
Other terms you will run into from time to time are called a “record high minimum” and a “record low maximum”. A record high
minimum is the coldest high temperature experienced on a certain date while a record low maximum is the warmest low temperature
experienced on a certain date. These can occur during exceptional periods of warm or cold weather.