Temperature is the second-most powerful extraction variable after grind, and far easier to control. Yet most home brewers guess. Here is what the numbers do, where the conventional wisdom comes from, and when to ignore it.
Target temperatures by method
These are starting points for medium roasts. Light roasts generally want the upper end; dark roasts the lower.
| Method | Target | Why |
|---|---|---|
| Espresso | 90–96°C | Machine-dependent; boiler temp ≠ brew temp |
| V60 / pour over | 92–96°C | High end for light roasts |
| Chemex | 93–96°C | Thick filter needs more heat |
| AeroPress | 80–96°C | Wide range; low temps reduce bitterness |
| French press | 92–96°C | Full immersion, forgiving |
| Moka pot | Boiling in the base | Pressure raises the effective temp |
| Cold brew | 4–20°C | Time substitutes for heat |
What temperature actually does
Hotter water dissolves compounds faster and more completely. Raising brew temperature from 90°C to 96°C increases extraction yield by roughly 2 to 4 percentage points at the same grind and time — enough to move a cup from sour to balanced.
But it is not a linear dial toward "better." Beyond about 96°C, you extract more of the harsh, astringent compounds that were previously locked in the cell walls. Below about 88°C, under-extraction leaves the cup sour and hollow no matter how long you brew.
Does boiling water ruin coffee?
The old advice — never pour boiling water on coffee, it burns it — is mostly wrong for the reason usually given. Water at 100°C cannot "burn" anything; the maximum temperature is fixed. What it does is extract faster, which can over-extract a fine grind.
The real reason the advice survives: with a coarse supermarket grind, boiling water in a French press produces a bitter cup within four minutes. That is over-extraction, not burning. Drop to 92°C or coarsen the grind and the same water is fine.
The one genuine caveat is that water straight off the boil loses dissolved oxygen, which some tasters claim flattens the cup. Let it sit 30 seconds and the objection disappears.
Hitting a target without a thermometer
Boiling water at sea level is 100°C. Ambient room temperature is around 20°C. A room-temperature ceramic pour-over cone absorbs a lot of heat. Practical approximations that get you within 2°C:
- Boil, then wait 45–60 seconds → roughly 93–95°C. This is the standard rule and it works.
- Boil, pour into a cold mug, then into the brewer → roughly 88–90°C.
- At altitude, water boils lower. At 1500 m it boils at 95°C, so a full boil is already near the top of the range.
- Pre-heat the brewer and the cup. An unheated V60 drops your water temperature by 5°C or more during the pour.
Espresso is different
On an espresso machine the boiler temperature is not the brew temperature. Water loses heat travelling to the group head, and the puck itself starts at room temperature. A machine set to 93°C may deliver 89°C at the puck on the first shot and 92°C on the third.
This is why the first shot of the day tastes different from the fourth. It is not superstition — it is thermal stabilisation. If you want consistency, flush the group head before the first shot.