"Nepenthes rajah" is a montane species or "highlander", growing at altitudes ranging from 1500 to 2650 m. As such, it requires warm days, with temperatures ranging (ideally) from approximately 25 to 30 ℃, and cool nights, with temperatures of about 10 to 15 ℃. The temperatures themselves are not vital (when kept within reasonable limits), but rather the temperature drop itself; "N. rajah" needs considerably cooler nights, with a drop of 10 ℃ or more being preferable. Failure to observe this requirement will almost certainly doom the plant in the long term or, at best, limit it to being a small, unimpressive specimen.