Weather Instruments

Rain gauges are essential weather tools for professional and amateur meteorologists, but their usefulness goes far beyond weather buffs. Gardeners and farmers have an innate need to know how much rain has fallen from the skies in order to keep their plants and crops healthy. And there's also those that are just plain curious about the amount of rain that falls. A simple rain gauge, sometimes called a pluviometer (in scientific terms from the Latin for rain and meter) or udometer (from the Latin for wet and meter) was first used by the ancient Greeks. Today these devices can be of three main designs: a single tube of 1-5” capacity, an inner cylinder that spills into a bigger outer reservoir when the inner one reaches capacity, or an unlimited self-tipping mechanism.

No matter what the design, all must be placed level in an unobstructed location away from houses, trees, and garages with no overhead obstacles. Many are secured to a stand on the top of a fence so they don't blow away during a big storm. Place rain gauges at a distance that is at least 2 x the height of nearby objects. For example, rain gauges should be 20 feet away from a 10-foot tree.

Take rain gauge readings daily, preferably at the same time and empty the reservoir after reading. For many rain gauges, once the inner tube fills up with rain, then it automatically overflows into the larger reservoir. To measure the rain in the larger reservoir, empty the full inner tube, pour the water from larger reservoir into smaller tube and measure. Keep pouring out the inner tube when full and repeat the measuring. Calculate the total rainfall by adding the total rain poured into the inner tube + the initial amount.

When measuring rain in some gauges, a curve will form on top of the water and may cause some confusion about the true reading. This is normal, and the measurement should be from the bottom of curve (or meniscus) for the most accurate result.

If rain gauges are going to be used to measure the amount of melted snow in winter, check the durability of it to make sure it does withstand freezing temperatures. Some rain gauges recommend that the inner tube and funnel be removed for snow measuring. The snow is melted and decanted into the inner cylinder for a measurement.

Rain gauges that are manually checked often are available in over-size models that are easier to read from a distance. Others have designs that magnify the numbers when water is in the cylinder.

If squirrels are a problem chewing up plastic models, choose glass and brass ones.

Watch for leaves, pine needles, spider webs and other debris that could distort rain readings inside the cylinder.

Rain gauges are very useful features in the garden and can often be an attractive architectural accent, too.