How do you read a maximum minimum thermometer?

Each side is read at the bottom of the marker that has been pushed upward since the last reading. Don't read the colored fluid where it is at that time. That would only give you the current temperature.

The bottom of the maximum marker is at the highest point that it was pushed to at the warmest time since the last reset, and the base of the minimum marker is where the liquid reached at the coldest time.

The markers need to be reset at the same time each day with a magnet. Drag the markers back so they are both sitting on top of the silver Mercury near the bottom of the tube. Horizontal thermometers are reset by turning them to vertical.