A rectal thermal monitor for transrectal prostate temperature measurement includes a handle arranged in a proximal end portion of the monitor for gripping by a user, an elongate shaft extending from the handle, and an expandable distal probe portion arranged on a distal end of the shaft. The distal probe portion is arranged at a position opposite the handle portion, and is shaped to facilitate insertion through an anal sphincter and into a rectum of a patient. A cover element, is provided for covering at least a portion of the distal probe portion, and is made from a resilient material. A temperature sensing element is arranged within the distal probe portion, beneath the cover element, and is adapted and configured to sense a temperature of the prostate of the patient through the rectum wall of the patient. Further, and actuator can be provided to actuate the expandable distal probe portion, to increase a diameter thereof.