• Sour French press coffee in cold weather is usually caused by under-extraction due to cooler water, a too-coarse grind, or a rushed steep time. The fix is to control your water temperature, adjust grind size, and give the coffee enough time to extract. This pattern solves most cold-weather sourness issues.
• Cold water and cold equipment drop brew temperature, causing sour, under-extracted coffee.
• Use water just off the boil (200°F/93°C) and preheat your press.
• Grind slightly finer and steep longer (4 minutes) to balance extraction.
• Adjust your coffee-to-water ratio if the brew still tastes weak and sour.