About the Measurements: Rainfall

The rain gauge funnel occupies the upper central part of the Davis Vantage Vue weather station. It is important to realise that the rain gauge measures the amount of rain, not whether it is raining!  A funnel catches the rain which drips into a counter balanced tipping spoon. When the spoon is nearly full it tips, clicking a micro-switch, and the spoon empties. Each tip represents 0.2mm of rain. That means that if it is raining hard the buckets fill and empty frequently and the data will indicate continuous rain. However for light rain or drizzle the bucket may only fill after a time so for most of the time it will look like the weather is dry! Also early morning dew might just be enough to fill the bucket and cause it to tip – so if you see 0.2mm of rain indicated for the early morning on a dry day – that’s probably why!

In windy conditions it is likely that the airflow around the weather station causes the rain amounts to be in error and probably under estimated.