An apparatus (300, 400, 500) comprising a magnetic resonance imaging system (302), the magnetic resonance imaging system comprising: a magnet (306) adapted for generating a magnetic field for orientating the magnetic spins of nuclei of a subject (310) located within an imaging volume (308); a radio frequency transceiver (320) adapted for acquiring magnetic resonance data (346) using a radio frequency coil (318); a computer system (336) comprising a processor (338), wherein the computer system is adapted for controlling the apparatus; and a memory (342, 344) containing machine readable instructions (354, 356, 358, 360, 362), wherein execution of the instructions cause the processor to perform the steps of: acquiring (100, 204) magnetic resonance data using the magnetic resonance imaging system, wherein the magnetic resonance data comprises transverse relaxometry data, and calculating (102, 206) the temperature of the subject within a temperature measurement volume (332) in accordance with the transverse relaxometry data.