At low temperatures, the air inside the capsule can contract and draw the membrane down causing a “run away.” This starts happening at about 4°C, 40°F. Cold temperatures also harden the drip tube which increases this effect. At hot temperatures, the opposite can occur. This doesn’t start happening though until 30° C, 86° F – and doesn’t make that much difference only slightly delaying the drip and going back to normal as soon as the temperature drops.