A thermometer helps while you are learning what temperature feels like, and most people stop using one.
The targets
Stop stretching at 37 °C — body temperature, when the jug still feels neutral.
Stop steaming at 60 to 65 °C — when the jug becomes uncomfortable to hold for more than a second or two.
Why not hotter
Above 70 °C, whey proteins denature and lactose sweetness is lost permanently. Milk scalded to 80 °C tastes flat and slightly eggy, and it will not be sweet again.
Many people steam far too hot because they want the drink to stay warm. It costs the flavour.
The hand method
Wrap your hand round the jug. When you cannot hold it comfortably, you are at about 60 to 65 °C.
This is accurate to a few degrees with a little practice, and it is instantaneous — no probe in the way of the vortex.
Types if you buy one
Clip-on dial — cheap, slow to respond, gets in the way of the vortex.
Digital probe — faster, still an obstruction.
Infrared — no contact, and it reads the surface rather than the body of the milk.
The honest recommendation
Buy a cheap clip-on, use it for two weeks to calibrate your hand, then take it off.
Steaming by feel is faster and lets you keep both hands where they need to be.
Last reviewed 8 August 2026