The most common rain gauge used today by official forecasters and airports was invented over 100 years ago. As you can see in the graphic, it consists of a large cylinder with a funnel and a smaller measuring tube inside of it. The official rain gauge has a tall cylinder with a funnel at the top that collects water into a measuring tube that has exactly one-tenth the cross sectional area of the top of the funnel. The reason for the smaller measuring tube is so that more precise precipitation measurements can be made due to the exaggeration of the height of water in the tube. For example, one-tenth of an inch of rainfall would actually fill an inch of the measuring tube. A special measuring stick inserted into the measuring tube takes into account the vertical scale exaggeration. This exaggeration allows meteorologists to make very precise measurements to one-hundredth of an inch. The official rain gauge measures up to an inch of rain in the inter tube. If rainfall exceeds 1 inch, water overflows into the cylinder surrounding the measuring tube. The observer takes the water in the cylinder and very carefully pours it into the measuring tube after emptying the tube. The observer then adds 1 inch to the measurement of water in the cylinder to obtain the final rainfall amount. (One inch is the amount in the inner tube before spilling over into the outer cylinder)

Measuring Precipitation in the form of Hail or Snow requires the removal of the inner tube and the funnel. Ice and snow is collected in the outer cylinder and then melted for a Precipitation reading.

Start logging precipitation with the OFFICAL RAIN GAUGE.