Get an adult to cut off the top 1/3 of a clear plastic fizzy drink bottle. Take the top off the bottle and invert the top third into the lower 2/3 of the bottle (it now acts as a funnel for collecting the rain water).
Put some pebbles into the bottom of the bottle then secure the two parts of the bottle together using tape. This will prevent it from coming apart and will reduce the amount of collected water that is lost through evaporation
Either stick the clear plastic ruler to the side of the bottle with sellotape just above the level of the pebbles or you can draw a scale onto some masking tape using the ruler then stick the masking tape straight onto the bottle.
Fill the bottle with water up to the ‘0’ at the bottom of your measuring scale or ruler. This becomes the bottom of the rain gauge.
Put the gauge in an open area where it is exposed to rain but where it won’t be easily knocked over by the wind, parents or pets.
Monitor rainfall each day by reading how many millimeters the water level has risen. You can plot this on a chart to see if it’s increasing or decreasing.
Before a big downpour, make predictions on how many millimeters of rain is going to fall. Get everyone in the family to guess then see who’s closest.
The funnel of your rain gauge is actually a miniature water catchment (see the section on Water Catchments). It is an area onto which rain falls, drains off and is collected in a storage tank (in this case your fizzy drink bottle).