Two things, at the two moments you know them: the forecast low and the window before bed, and in the morning whether it was too cold. After a couple of weeks the chart below says how low you can go with the window open.
Two things, at the two moments you know them: the forecast low and the window before bed, and in the morning whether it was too cold. After a couple of weeks the chart below says how low you can go with the window open.