A weather diary is a single page with 31 boxes, where your child writes down how cold it is, what the weather looks like and how long the day is. It takes two minutes each morning and needs only a thermometer, a pencil and a weather app. But after a month, something odd happens. When the full page lies on the table, the cold is not what changed most. Something else shrank, a little every single day, so quietly that almost nobody noticed.
What happens to the weather over a month?
Weather is what is happening in the air around us right now: temperature, clouds, wind, rain and snow. Most of us picture autumn as a steady staircase down, each day a bit colder than the last. Yet the windowsill can be icy one morning and almost mild the next. A cloudy night holds warmth in like a blanket, while a clear night lets it escape, which is why mornings are often the coldest time of day. Read more in Why is it coldest in the morning?
Day length is different. It is not decided by clouds, but by the tilt of the Earth as it travels around the Sun. In autumn our part of the planet leans away from the Sun. In Oslo, around five minutes of daylight disappear each day in late October, and further north it goes even faster.
It is not the cold that changes most steadily in autumn. It is the light.
When the clocks go back an hour on 25 October, sunrise and sunset jump on the clock, but the day itself does not get any longer. All our autumn experiments are collected in The autumn outdoor laboratory.
Try it at home: one page, 31 boxes
Suitable for: 5–12 years
You need an outdoor thermometer, a large sheet of paper, pencils, a ruler and a weather app that shows sunrise and sunset.
- Hang the thermometer in the shade.
- Read it at the same time every morning and write it in the box.
- Draw a symbol for the weather.
- Work out the day length from sunrise and sunset.
- Colour a blue bar for temperature and an orange bar for day length.
- After 31 days, look at all the bars together.
Want to measure rain too? Build a rain gauge from a plastic bottle. And what happens if you draw a line across the tops of each set of bars: which line turns out straighter?
Questions to wonder about
- Why might a cloudy November day be warmer than a sunny one?
- If the days are getting shorter now, when do you think they start getting longer?
- Why do the days shrink faster in the far north of Norway than in Oslo, when it is the same Sun?
Every child is made of good atoms
When the page is full, 31 small measurements hang on the fridge, each one a moment when your child stood by the window, felt the cold and looked closely. Every child is made of good atoms, and every child can discover that the quiet, steady light says more about the season than the jumpy cold.
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