© 2018 Author(s). Spin-orbit torque (SOT) switching and retention properties in Co/Pt multilayer nanowire structures with various widths w down to 20 nm and the temperature dependences of the performance in the nanowire device with w = 20 nm are studied. Switching current Isw scales down as w is reduced. The nanowire devices show high thermal stability factor Δ > 100 for all the widths at room temperature. In the 20-nm-wide device, while a magnetization can be switched by current from -50 to 125 °C with a marginal increase in Isw as the temperature decreases, Δ of more than 100 is kept up to 125 °C. These results indicate that SOT-switching devices using Co/Pt multilayers are scalable in nanoscale dimensions and can operate over a wide range of temperatures, offering high potential for a wide variety of applications including automobile and aerospace.