How do you manually tell the temperature?

In the winter its easy.

Technology wise: Below 49 and it takes half an hour for the computer to start up. Below 32 and its an hour or more. In the twenties - make a huge pot of coffee, start in the morning and by afternoon you might get online.

By nature: We look at the shrub outside the one window. The colder it is the lower and more closed the leaves are. Todays temperature forecast. Don't be crazy, stay indoors!