The best historical precipitation data

Precip automatically measures rain amounts with precision and accuracy. This guide serves as a simple overview of how the technology behind Precip works.

We use high resolution radar, and quality controlled gauge data to observe precipitation and model accumulation on the surface of the earth. We continually refine our data to be the most accurate and useful source for monitoring rainfall, snow, and other types of precipitation.

What goes into the analysis

Unlike most other weather data sources, Precip is able to provide an accurate representation of what actually happened at a specific location. Many users are accustom to using data from traditional weather APIs that simply archive historical records of what was forecasted. Precip provides real oberservational data, not just forecasts.

We utilize data from multiple public sources, including 180 doppler radar stations and a quality controlled network of rain measurement stations.

That raw data gets processed through a series of scientific models that translate raw information into easy to understand rainfall amounts. Part of that process includes aligning data from multiple sources into the correct hourly time periods for reliable analysis.

The final stage of processing is creating a proprietary ensemble of the various model outputs to deliver the highest quality blend of low latency and highly refined data all correctly projected for geospatial analysis.

Coverage area & resolution

Our data currently covers the United States, Canada, and some of Mexico with other regions becoming available upon request.

An important consideration is that our rainfall measurements in the US quantify rainfall for an area of roughly one half mile squared, or 160 acres. In Canada it is approximately 1 square mile or 250 hectares. Depending on the particular patterns of any given rainfall event, there could be varying amounts of precipitation even within an area that small. Our models will provide an average value for the area represented.

Why observations beat forecasts

Most apps that show rain totals only show the most recent forecast amount before the actual rain. Precip uses actual radar and ground-truth observations of actual rain as it happens to create the most accurate possible rainfall totals.

By using real observations, Precip is able to provide hourly totals that are 60% more accurate and 275% better rainfall detection than NOAA's High Resolution Rapid Refresh forcast.

Performance and benchmarks

Our estimates are the best available, but no rainfall estimate is perfect. In fact, rain gauges themselves can often provide inaccurate measurements. See our blog post about that here. One example is the estimate that wind turbulence causes a 2-10% average error rate when using gauges to measure rainfall. Our models account for wind and evaporation even though rain gauges do not.

The figures below are excerpts from a 2023 benchmarking study that compared Precip to the High Resolution Rapid Refresh forecast model output and the Integrated Surface Database ground observations. The report analyzes accuracy metrics for rainfall events at various accumulation thresholds as measured by the corresponding gauge data.

Questions or comments?

We'd love to hear from you! Email us at [email protected].