Temperature of neutral gas in positive columns increases considerably even in the glow regime with relatively lower currents as the radius of columns becomes smaller than a few milli meters. To study the effect on discharges, measurements are made by using a small thermocouple sphere in He, He-Ne mixture and Ne discharges. For given current and pressure, the temperature becomes higher as the gas has a higher ionization potential and as the pressure is decreased for a constant current. The equilibrium temperature and the rates of heating and cooling of the positive column are found to be dependent on the wall. Influence of the gas temperature on the characteristics of discharges in small-bore tubes is discussed by using macroscopic equations.