What it teaches
That weather is measured, and with what. A rain gauge gives millimetres, a thermometer gives degrees, a wind vane gives a direction — and cloud cover is judged by eye, which is worth saying because not everything in science has an instrument.
The storm is the best one: counting the seconds between the flash and the bang gives roughly a kilometre for every three, which is a measurement a child can make with nothing at all.
How it works
Something to measure appears and the instruments are the answers. Twelve of them, from a rain gauge to a barometer, and one that needs no instrument at all: cloud cover is judged by eye.
What to look for
A rain gauge is a straight-sided jar and a ruler. A week of readings on the fridge is the whole of this game, done properly.