Question

When weathercasters talk about normal high or normal low temperatures for a given day, they are referring to

Answer 1

the average high or low temperature for that day based on historical weather data collected over a period of time, typically 30 years. This is also known as the climatological normal or simply "normal" temperature. It serves as a reference point for evaluating current and future weather conditions. For example, if the forecast high temperature for a certain day is 10 degrees below the normal high temperature, it is likely to be a very cold day.

Answer 2

Typically the low temperature is before sunset but quite often when forecasters talk about the temperature for any day they are referring to the low temperature. A forecast (high and low) represent the predicted max and min temperatures during the midnight to 11:59 pm. The temperature in a forecast is given to describe the forecasts maximum and minimum temperature or if you would prefer in some cases the temperature at a specific time.

(Hope this helps)