The top RED line is the observed record maximum (high) temperature on a daily basis for Lincoln, Nebraska.
The smoother sloping RED line is the normal maximum (high) temperature on a daily basis for Lincoln

The smoother sloping BLUE line is the normal minimum (low) temperature on a daily basis for Lincoln.
The bottom BLUE line is the observed  record minimum (low) temperature on a daily basis for Lincoln.
 

The top of each green bar is the record maximum temperature, and the bottom of each green bar is the record minimum temperature.
For example, on January 12, the record maximum temperature is 64 F and the record minimum temperature is -33 F.

The sloping RED line is the normal maximum (high) temperature on a daily basis for Lincoln
The sloping BLUE line is the normal minimum (low) temperature on a daily basis for Lincoln.

The top of each green bar is the record maximum temperature, and the bottom of each green bar is the record minimum temperature.
For example, on January 12, the record maximum temperature is 64 F and the record minimum temperature is -33 F.
 

The following figure covers only a portion of the year (January through April) and the individual vertical bars can be more easily seen.