Around 60 to 65 °C (140 to 149 °F). That is hot enough to be a hot drink and below the point where milk starts to taste of itself in a bad way.
Why the ceiling matters
Milk contains lactose, and heat breaks it down. Below about 65 °C (149 °F) the milk tastes sweeter as it warms, because heat makes the existing sweetness more perceptible. Past roughly 70 °C (158 °F) the proteins denature and the lactose starts to scorch, and the flavor turns flat, cooked and faintly eggy.
Once that has happened it cannot be undone. Overheated milk is overheated.
How to judge it without a thermometer
Put your hand on the side of the pitcher throughout. Stop when it becomes uncomfortable to hold — around three seconds before you would have to let go. That lands most people between 60 and 65 °C (140 and 149 °F), and it works because human skin is a surprisingly consistent sensor in that range.
Almost every professional does it this way. A clip-on thermometer is a good idea for the first two weeks, until your hand learns the number.
Why serving temperature disappoints people
A drink at 60 to 65 °C (140 to 149 °F) is noticeably cooler than tea or drip coffee, and people used to those often think a flat white is lukewarm. It is not — it is at the temperature that keeps the milk tasting sweet. Warming the cup helps considerably, because a cold ceramic cup takes several degrees out of the drink immediately.
Why people ask for it hotter
Customers often want a drink that stays hot on a commute and associate heat with quality, so cafés are asked to push past 70 °C (158 °F). It is a real trade of flavor for temperature. Preheating the cup is the better way to a hotter drink: it keeps the drink warm without cooking the milk. Re-steaming milk that has cooled will not foam and tastes cooked.
If it never tastes sweet
Old milk near its date has begun to sour and will not taste sweet; skim milk’s lower fat makes sweetness read thinner; and standard oat and soy milks carry far less sugar than dairy, though barista editions often add some.
Plant milks want less
Oat and soy have a narrower window and collapse sooner. Stop a few degrees earlier than you would with dairy — around 55 to 60 °C (131 to 140 °F).
What people want to know
Can I reheat milk that has gone cold?
You can heat it and it will not foam properly again. Re-steaming already-steamed milk gives thin, bubbly foam and a cooked flavor. Steam what you need and pour it.
Why does café milk taste sweeter than mine?
Usually temperature. Home users overheat, and heat is what destroys the sweetness. Stopping five degrees earlier is often the whole difference.
Last reviewed 30 October 2026