<P> What thermal comfort humans, animals and plants experience is related to more than temperature shown on a glass thermometer . Relative humidity levels in ambient air can induce more or less evaporative cooling . Measurement of the wet - bulb temperature normalizes this humidity effect . Mean radiant temperature also can affect thermal comfort . The wind chill factor makes the weather feel colder under windy conditions than calm conditions even though a glass thermometer shows the same temperature . Airflow increases the rate of heat transfer from or to the body, resulting in a larger change in body temperature for the same ambient temperature . </P> <P> The theoretical basis for thermometers is the zeroth law of thermodynamics which postulates that if you have three bodies, A, B and C, if A and B are at the same temperature, and B and C are at the same temperature then A and C are at the same temperature . B, of course, is the thermometer . </P> <P> The practical basis of thermometry is the existence of triple point cells . Triple points are conditions of pressure, volume and temperature such that three phases are simultaneously present, for example solid, vapor and liquid . For a single component there are no degrees of freedom at a triple point and any change in the three variables results in one or more of the phases vanishing from the cell . Therefore, triple point cells can be used as universal references for temperature and pressure (see Gibbs phase rule). </P> <P> Under some conditions it becomes possible to measure temperature by a direct use of the Planck's law of black - body radiation . For example, the cosmic microwave background temperature has been measured from the spectrum of photons observed by satellite observations such as the WMAP . In the study of the quark--gluon plasma through heavy - ion collisions, single particle spectra sometimes serve as a thermometer . </P>

Briefly explain the reason for measuring temperatures and rainfall figures