Cold brew has no heat, and the temperature it does have still matters.
Fridge versus room temperature
Refrigerated (4 °C, 39 °F): slower extraction, 16 to 24 hours, and a cleaner, more delicate result. Also safer for a long steep, since nothing is growing.
Room temperature (20 °C (68 °F), 68 °F): faster, 8 to 12 hours, and generally a heavier, sweeter, slightly more fermented character.
Neither is wrong. They are different recipes and the time must change with the temperature.
Why the flavor differs
Extraction rate is temperature-dependent for every compound, but not equally. Warmer steeping pulls out more of the heavier, sweeter material relative to the delicate aromatics, which is why room-temperature cold brew tastes rounder.
The safety point
A long steep at room temperature is a warm wet environment. Twelve hours is fine; leaving it for two days on a warm countertop is not. If you want a long steep, use the fridge.
Starting with hot water
Some recipes bloom with a splash of hot water before adding cold. It speeds things up and shifts the profile towards hot-brewed coffee, which rather defeats the point if you chose cold brew for its low acidity.
Practical recommendation
Fridge, 1:8 for concentrate, 16 hours. Then adjust time rather than temperature.
What people want to know
How long does cold brew concentrate keep?
About a week to ten days, sealed in the fridge. Filtered well and kept cold, it stays drinkable; once it tastes sour or flat, it is past its best.
Last reviewed 30 October 2026