What is the purpose of an isotherm on a weather map?

An isotherm is specifically designed to connect points on a weather map that show the same mean temperature. This graphical representation allows meteorologists and the general public to easily visualize temperature distributions across a given area. By using isotherms, one can identify temperature gradients, which can be critical for understanding weather patterns, forecasting, and assessing conditions such as heatwaves or cold fronts.

In contrast, other lines on weather maps serve different purposes, such as isohyets for rainfall or isobars for pressure, but isotherms are uniquely tied to temperature. Thus, the definition of an isotherm aligns perfectly with the notion of connecting places with equal mean temperature, making this choice the correct one for understanding the function of isotherms in meteorology.