Numerous applications call for electronics capable of operation at high temperatures where conventional Si-based electrical devices fail. In this work, we show that graphene-based devices are capable of performing in an extended temperature range up to 500 °C without noticeable thermally induced degradation when encapsulated by hexagonal boron nitride (hBN). The performance of these devices near the neutrality point is dominated by thermal excitations at elevated temperatures. Non-linearity pronounced in electric field-mediated resistance of the aligned graphene/hBN allowed us to realize heterodyne signal mixing at temperatures comparable to that of the Venus atmosphere (∼460 °C).