November

Pair of thermometers to measure daily maximum and minimum air temperature at weather stations.
A maximum thermometer (above) is a thermometer used in meteorology to measure the maximum air temperature over a given time interval, usually 24 hours. The most commonly used thermometer is a glass mercury thermometer with a tapered capillary section above the container. The mercury penetrates this cross-section only when the temperature rises, and when the temperature falls the mercury column breaks at this point, and the length of the mercury column in the capillary determines the maximum temperature reached. After the reading is taken, the thermometer is adjusted for the next measurement by vaulting (the same principle underlies the medical thermometer).

A minimum thermometer (below) is a thermometer used in meteorology to measure the minimum air temperature over a given time interval, usually 24 hours. The most commonly used thermometer is the glass alcohol thermometer, which has a small dark-coloured glass rod (index) placed in a capillary inside the column of thermometer liquid, which is pulled towards the container by the surface tension of the alcohol surface as the temperature drops. As the temperature rises, the index is bypassed by the thermometer liquid, so that its position remains unchanged. When the reading is taken, the index moves towards the end of the alcohol column by tilting.

The two thermometers are installed in the meteorological screen in a horizontal position so that the measurement is not affected by the force of the earth's gravity.