Suppose you are working on weather prediction, and use a learning algorithm to predict tomorrow's temperature (in degrees Centigrade/Fahrenheit). Would you treat this as a classification or a regression problem?

This is a subject of supervision and learning, according to the weather, predict the future of the weather, because the predicted temperature is continuous value, so the regression problem such as discrete values, the classification problem, and the forecast for the next day (like Sunny, overcast, rain) is classified. So, the correct choice is regression.