# Help me understand rain gauges

**URL:** <https://boards.straightdope.com/t/help-me-understand-rain-gauges/498990>\
**Category:** Factual Questions\
**Created:** [June 7, 2009, 5:22am UTC](https://boards.straightdope.com/t/help-me-understand-rain-gauges/498990 "2009-06-07T05:22:32Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![happywaffle](https://avatars.discourse-cdn.com/v4/letter/h/ee59a6/32.png) [@happywaffle](https://boards.straightdope.com/u/happywaffle)\
**Post date:** [June 7, 2009, 5:22am UTC](https://boards.straightdope.com/t/help-me-understand-rain-gauges/498990/1 "2009-06-07T05:22:32Z")

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In short: how large a diameter does a gauge need to have for it to be giving an accurate indication? I’m surprisingly confused by the fact that water is distributed in discrete drops, which makes me think that a given spot might receive less water in a given period than a spot right next to it. Does the ~1-inch diameter of my little rain gauge account for this?

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**Author:** ![Napier](https://avatars.discourse-cdn.com/v4/letter/n/ce73a5/32.png) [@Napier](https://boards.straightdope.com/u/Napier)\
**Post date:** [June 7, 2009, 11:20am UTC](https://boards.straightdope.com/t/help-me-understand-rain-gauges/498990/2 "2009-06-07T11:20:07Z")

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The problem is that rain arrives in discrete drops and that makes a rain gage’s measurement change in that size increment. If you add one drop to your gage, how much does it change? Even a one inch diameter gage is not going to look much different after the arrival of one more drop.

A spot on the ground can receive different water for this reason. That’s why if it barely sprinkles, the patio becomes polka-dotted. But rain of this quantity is generally not important anyway. To the extent that rain waters the plants, the ground absorbs and distributes water on a larger-than-droplet scale. To the extent that it warms or cools or cleans the air, that’s always mixing around anyway.