A method and apparatus are disclosed for controlling temperature of a plant comprising plural temperature control zones, wherein an effective control parameter for a first zone for which a signal representing measured temperature is available is produced according to an algorithm relating measured temperature, a desired temperature and a control parameter associated with a device affecting temperature in the first temperature control zone, the effective control parameter is summed with an offset value representing a proportional offset of the effective control parameter of a second temperature control zone relative to the effective control parameter of the first temperature control zone and the result is applied to control a device affecting temperature in the second temperature control zone. Advantageously, the offset value comprises a fixed amount and a variable amount, the variable amount accounting for dynamic differences in temperature control characteristics of the first and second temperature control zones.