Christine J. Park, age 9, of Williamsport, Pennsylvania, for her question: 

How can almanacs predict the weather?

Last year, August was warm and December was cold over most of the land. The same thing has been happening for many, many years. So we can expect it to happen this year and next year. People who prepare almanacs know when to expect the spring and summer, fall and winter seasons, just as we do. But they go into more detail and predict the weather for each day of the year. They do this by studying the weather details that happened on each date through many years. What happened in the past is likely to be repeated    so there is a good chance that the almanac will be right.

The Weather Bureau has kept detailed weather reports through some 50 years. Sup¬pose these records show that 30 of these years brought thundershowers to Williamsport on August 21. What happened so many times in the past is quite likely to happen again. So the almanac predicts it and there is a good chance of thunderheads on August 21. But this is not absolutely certain. The weather has a mind of its own and next August 21 there may not be a single cloud in the sky all day.