The temperature here varies from day to day between cold and very cold (by my standards, at least). There is, however, a significant practical difference between the two in that if it's only cold I just need a coat whereas if it's very cold I need a hat, scarf, and gloves as well.
In order to tell the temperature before I go outside, I keep a cup of water on my balcony easily visible from inside. If I get up in the morning and the water is frozen, I know it's going to be very cold outside. This system is working pretty well so far, but I'll have to think of something else if I ever need to differentiate between very cold and extremely cold.