Please indicate what the upper limit is for both measurements.
That depends on whether you are talking about a generic RFID transponder or one specifically designed to handle higher temperatures and pressure. Generally speaking, a generic transponder—active or passive—can withstand temperatures of no more than 180 degrees Celsius (356 degrees Fahrenheit). That's because they use solder to connect the chip to the antenna, and to connect components to the circuit board on active transponders, and the most commonly used solders melt at approximately 180 degrees Celsius.
There are specially designed tags that can withstand greater temperatures by using special solders and other means to protect the transponder from high temperatures. Technologies ROI (TROI) has designed two such passive tags: the Armored-RFID and the Weldable option World (WoW) tags. Both consist of EPC Gen 2 inlays clad in stainless steel. These durable tags are designed to be able to withstand temperatures of 600 degrees Fahrenheit (316 degrees Celsius), and can also be whacked with a sledge hammer without damaging the transponder (see Armored-RFID Tag Loves to Get Hammered).
Keep in mind that surviving high temperatures for an hour or two is different than operating at high temperatures. Most silicon chips can not operate at temperatures above 125 degrees Celsius (257 degrees Fahrenheit), so you will not be able to read the tag if the temperature hits that level.
—Mark Roberti, Founder and Editor, RFID Journal