About the data
One clear number,
with context.
Rain by Zip turns detailed weather datasets into an approachable rainfall estimate for a selected U.S. location and time period.
What the number represents
The result is an estimate for the weather-data grid cell nearest the selected coordinates. A grid cell covers an area rather than a single backyard. That distinction matters because a brief thunderstorm can soak one neighborhood while leaving another nearby almost dry.
Recent rainfall
Today, Past 24 Hours, and Past 7 Days load together for the displayed location. Where current NOAA Multi-Radar Multi-Sensor (MRMS) analysis is available, the rolling 24-hour total uses approximately 1 km radar precipitation data. The same total is reconciled with hourly Open-Meteo estimates before calculating Today and Past 7 Days, so overlapping periods agree. Earlier completed days use historical estimates. All three totals end at the latest completed analysis hour; the current incomplete hour is not counted. Today starts at midnight in the selected location’s timezone. If current radar is unavailable, the page labels the readings as model estimates. Radar precipitation can include the liquid-water equivalent of snow.
Historical rainfall
Custom-date reports use Open-Meteo’s historical weather service. The site sums daily rain estimates between the chosen start and end dates. Historical products combine observations with weather-model analysis to provide consistent coverage, including places without a reporting gauge nearby.
Year-to-date rainfall and normal
The year-to-date line graph compares cumulative ERA5 rainfall for this year with a 1991–2020 average of the same calendar days, using Open-Meteo’s historical service and the same weather-model grid for both lines. February 29 uses only leap years in the baseline. This is a gridded reanalysis average, not an official NOAA station normal. Both lines stop at the same published date, about seven days behind today, to avoid treating incomplete data as zero. The recent cards use a different, more current radar/model blend and are not expected to match this slower climate dataset exactly.
Why another gauge may disagree
- A physical gauge measures only the rain falling into that instrument.
- A weather grid represents an area and may smooth out a small, intense storm.
- Wind, trees, buildings, gauge placement, and maintenance can affect physical measurements.
- Weather datasets can be updated after additional observations and quality checks arrive.
Good uses and important limits
The site is useful for curiosity, gardening context, travel follow-up, and a quick sense of recent conditions. It is not a replacement for an official gauge record, flood warning, insurance document, engineering analysis, or regulated agricultural measurement.
Source documentation
Technical details are available in the NOAA MRMS documentation and the Open-Meteo documentation. Emergency weather information should come from the National Weather Service.
Who publishes and reviews Rain by Zip
The Rain by Zip editorial team maintains the explanations, featured location reports, source references, and calculation notes on this site. Data-driven values are generated from the identified weather services, while the surrounding guidance is written and reviewed for clarity, limitations, and responsible use.
Editorial review date: September 23, 2026. Corrections, source questions, or reports of a misleading explanation can be sent to webmaster@karnigventures.com. Material corrections are checked against the underlying source before the page or method is updated.