How Do Weather Stations Measure Rainfall?

Rainfall seems like a simple measurement, but getting it right requires careful mechanical design. The rain gauge on your weather station is a precision instrument that counts every drop, and understanding how it works helps you interpret the data correctly — and explains why your total never quite matches your neighbor's.

How does a tipping bucket rain gauge work?

A tipping bucket rain gauge funnels rain into one of two tiny buckets balanced on a pivot. When a bucket collects a calibrated amount of water — 0.2 mm of rainfall on metric Davis collectors, 0.01 inch on US ones — it tips, empties, triggers a magnetic pulse, and swings the other bucket under the funnel.

Step by step, it works like a tiny mechanical seesaw:

1. Rain falls into a funnel at the top of the gauge
2. The funnel channels water into one of two small buckets balanced on a pivot
3. When the bucket fills to the calibrated amount, its weight tips it down
4. The tip empties that bucket and positions the other bucket under the funnel
5. Each tip generates a magnetic pulse that the station counts
6. The station multiplies the number of tips by the tip size to calculate total rainfall

The process repeats for as long as it rains. The tipping bucket is also the only moving part doing real measurement work on most stations — the rest of the suite is solid-state, as covered in our guide to weather station sensors.

What rainfall values does the station report?

From bucket tips alone, a weather station derives everything it reports about rain: the daily total (tips multiplied by the tip size), the rain rate (calculated from the time between consecutive tips), and running storm, monthly, and yearly totals. No water is ever weighed or stored — only counted, one tip at a time.

• Rainfall today. The cumulative total since midnight.
• Rain rate. How fast rain is falling right now, derived from the interval between tips. A high rain rate means the bucket is tipping rapidly, which indicates intense precipitation.
• Rainfall this storm. The total for the current rain event; stations reset this after a defined dry period.
• Monthly and yearly totals. Accumulated from the daily totals, these gradually become your site's climate record.

These values are what you see on your console, in the WeatherLink app, and on your weather website's charts.

How accurate is a tipping bucket rain gauge?

A well-maintained tipping bucket gauge is accurate to within a few percent in ordinary rain. Accuracy drops in two situations: intense downpours, where water is lost during the tip itself, and strong wind, which carries drops past the funnel. Debris, insects, and an unlevel mount cause larger errors than the mechanism ever does.

The known limitations in detail:

• Undercatch in heavy rain. During intense downpours, some water is lost during the bucket tip itself, when neither bucket sits squarely under the funnel. Davis gauges minimize this with a fast-tip mechanism, but some undercatch is inevitable at extreme rain rates.
• Wind undercatch. Wind blowing across the funnel carries some drops past the opening — the stronger the wind, the more the gauge misses. In exposed locations this is the single biggest error source.
• Blockages. Leaves, debris, or insects in the funnel can block the water flow entirely. A blocked gauge stops reporting until it is cleaned.
• Splash. Large raindrops can splash out of the funnel, especially in gusty conditions.
• Leveling. The gauge must be level. If it tilts, the two buckets fill unevenly and the measurement drifts.
• Evaporation. In hot weather a tiny amount of water can evaporate before a bucket tips — negligible in practice, but real.

Why does a tipping bucket differ from a manual rain gauge?

A manual gauge collects and stores all the rain that falls into it, so you read the true depth directly — but only when you go out and check it. A tipping bucket trades a little accuracy for automation: it quantizes rain into fixed 0.2 mm steps but records the timing of every increment automatically.

That quantization means a shower that ends mid-fill leaves water sitting in the bucket, uncounted until the next rain tops it up — so individual events can read a fraction low while long-term totals stay honest. Manual and automatic gauges also rarely share the same exposure: different heights, different distances from walls and trees, different wind shelter.

Position usually matters more than the instrument. Two gauges a garden apart can legitimately disagree, especially in showery weather. For where to place a gauge — away from roof edges, overhanging branches, and wind shadows — see the weather station siting guide.

How do you maintain a rain gauge?

Rain gauge maintenance takes five minutes a few times a year: lift off the funnel, clear leaves and insects, rinse the buckets with clean water, confirm the gauge is level, and check that the buckets tip freely. A dirty or tilted gauge underreads long before it fails completely.

• Clean the funnel every few months, especially after leaf fall and pollen season. Remove any debris and rinse with clean water.
• Check for insects. Small insects and spiders like to nest in the funnel or around the tipping mechanism. A gentle rinse usually clears them.
• Confirm it is level. Place a small bubble level on top of the gauge and adjust the mounting if needed.
• Inspect after storms. Heavy rain, hail, or wind can knock the gauge out of alignment.

Rain gauge care slots neatly into a broader routine — our seasonal maintenance checklist covers the whole station in one pass.

How is rainfall displayed on your weather website?

Once your station uploads its tip counts to WeatherLink, a connected website turns them into readable rainfall data: the current rain rate, today's running total, historical charts by day, month, and year, and all-time records. Everything on screen traces back to those individual bucket tips inside your gauge.

Pro Weather, for example, shows:

• Current rain rate with an intensity indicator
• Today's total with a visual progress bar
• Historical charts showing daily, weekly, monthly, and yearly totals
• Records for the highest rain rate, wettest day, wettest month, and wettest year
• Email alerts when the rain rate crosses a threshold you define

If you have a Davis station and want your rainfall history on a live, modern website, Pro Weather connects in minutes and stores your data forever.

Common questions

Why does my rain gauge read less than my neighbor's?

Wind exposure is the usual culprit: a gauge on a breezy rooftop catches measurably less than one in a sheltered garden. Mounting height, nearby obstructions, and leveling all contribute — and in showery weather, rainfall itself varies over a few hundred meters, so both gauges can be right. If the gap is large and consistent in steady rain, check your level and funnel first.

How often should I clean my rain gauge?

Every few months is enough for most locations, with extra checks after autumn leaf fall and spring pollen season. It takes five minutes. A partially blocked funnel delays water reaching the buckets, which distorts rain rate readings and can undercount totals — and a fully blocked one records nothing at all while looking perfectly normal from the ground.

Can a rain gauge measure snow?

Not as it falls. Snowflakes pile up in the funnel and only register when they melt — hours or days later, minus whatever evaporates or blows away. Heated collectors solve this by melting snow on contact, but Davis gauges are not heated by default. Treat winter totals from an unheated tipping bucket as indicative rather than accurate.

How do I calibrate my rain gauge?

Drip a known volume of water slowly through the funnel and compare the recorded tips with what the math predicts for your collector size. If it is consistently off, most gauges — Davis included — have small adjustment screws under the buckets. The full procedure, including how much water to use, is in how to calibrate your weather station's sensors.