A cooktop appliance includes a top panel with a gas burner disposed on the top panel. The cooktop appliance also includes a grate with a plurality of fingers. The grate is removably positioned above the gas burner. The plurality of fingers includes a sensor finger. The cooktop appliance also includes a hermetically sealed temperature sensor mounted to the sensor finger of the plurality of fingers of the grate. The hermetically sealed temperature sensor includes a base, a sheath extending from the base to a rounded tip, and a contact pad in the base.