Temperature and re
An isotherm (from θερμη or thermē, meaning 'heat') is a line that connects points on a map that have the same temperature. Therefore, all points through which an isotherm passes have the same or equal temperatures at the time indicated. Generally, isotherms representing 5 °C or 10 °F temperaturedifferences are used, but any interval may be chosen.
An isogeotherm is a line of equal mean annual temperature. An isocheim is a line of equal mean winter temperature, and an isothere is a line of equal mean summer temperature.
An isohel (from ήλιος or helios, meaning 'sun') is a line of equal or constant solar radiation.