Data sources and attribution
Effective September 4, 2026
This page lists the sources behind every figure on WeatherTotals, what we take from each, and how we name them. Each figure on the site carries its own source and observation time.
Sources
| Source | What we take | How often | Licence |
|---|---|---|---|
| National Weather Service API (api.weather.gov) | Active alerts (winter, flood, severe thunderstorm and tornado), gridded cloud cover forecasts for dark-sky spots | Live, checked every 15 minutes | US public domain |
| NOAA Space Weather Prediction Center (services.swpc.noaa.gov) | Planetary Kp index (1-minute estimated and 3-hour official), 3-day Kp forecast | Every 15 minutes | US public domain |
| Iowa Environmental Mesonet of Iowa State University (mesonet.agron.iastate.edu) | Feed of NWS Local Storm Reports (spotter snow, rain, hail reports) | Live during events | Public domain; IEM asks for attribution |
| NOAA National Centers for Environmental Information (ncei.noaa.gov) | GHCN-Daily station observations (season and year to date, records) and U.S. Climate Normals 1991-2020 (averages) | Daily | US public domain, with citation |
| Iowa Environmental Mesonet of Iowa State University (mesonet.agron.iastate.edu), National Weather Service daily climate report | Yesterday's rain, month-to-date and year-to-date totals, 1991-2020 normals for each, and the date's record | Daily, checked every three hours | US public domain; IEM asks for attribution |
| NOAA National Centers for Environmental Information (ncei.noaa.gov) Storm Events Database | We use hail events (stone size, date, location, county, reporting source) to derive state and city hail maximums since 1996, monthly and yearly counts, and the 2005-2025 average. | Every one to two months, two to three months behind. | US public domain, with citation |
| NRCS SNOTEL (AWDB REST API) | SWE, snow depth, precipitation, medians from 1991-2020, station details, station history | Readings every 3 hours, history yearly | A US government work under 17 U.S.C. 105, so public domain |
| Climate Prediction Center, NOAA (cpc.ncep.noaa.gov) | RONI (Relative Oceanic Niño Index), 3-month values since 1950, used to classify El Niño winters | checked each spring after the winter closes | US public domain |
Source notes
The National Weather Service API provides current alerts and the cloud cover data we use to estimate whether aurora will be visible at dark-sky locations. We check it every 15 minutes.
The NOAA Space Weather Prediction Center gives us the planetary Kp index, both the 1-minute estimated value and the 3-hour official value, plus a 3-day forecast. This is the main measure we use for aurora strength.
The Iowa Environmental Mesonet of Iowa State University aggregates Local Storm Reports filed by NWS offices. These are spotter reports of snow, rain and hail, and we use them for immediate event totals. IEM asks for attribution, and we name them on every figure that uses their feed.
For season-to-date totals and records, we use daily observations from GHCN-Daily, maintained by NOAA National Centers for Environmental Information. Averages come from the U.S. Climate Normals 1991-2020, also from NCEI. We update these daily.
The National Weather Service daily climate report is a CLI product that each forecast office issues every morning for its airport stations. From it we take the previous day's rain, month-to-date and year-to-date totals, their 1991-2020 normals, and the record for the date. The feed comes through the Iowa Environmental Mesonet, which we credit on every figure it supplies.
The Storm Events Database is NCEI's archive of confirmed severe weather reports, covering the United States since 1950. We pull hail observations from it for the largest stone per state and city, monthly and yearly counts, and the 2005-2025 annual average. We refresh our pages when NCEI posts the annual files, about every month or two, covering events from two to three months earlier.
CPC publishes the Relative Oceanic Niño Index. From that index, the winters since 1950 with a strong El Niño classification are selected, and GHCN-Daily station records for those winters are compared with every other winter.
Public domain notice
The government-produced weather and aurora material on this site is prepared by NOAA offices, including the National Weather Service. Under 17 U.S.C. 105, those works are not subject to copyright in the United States. We give this notice under 17 U.S.C. 403. The material identified includes Local Storm Reports, alerts, gridded forecasts, Kp index values and forecasts, GHCN-Daily observations, and climate normals.
Citation
The providers above ask that their data be credited. The citations below are the ones each provider specifies. If you reuse a figure from this site, cite the original provider; a link back here is welcome but not required.
- Menne, M.J., I. Durre, R.S. Vose, B.E. Gleason, and T.G. Houston, 2012: An overview of the Global Historical Climatology Network-Daily database. Journal of Atmospheric and Oceanic Technology, 29, 897-910. GHCN-Daily, NOAA National Centers for Environmental Information, doi:10.7289/V5D21VHZ.
- NOAA National Centers for Environmental Information, 2021: U.S. Climate Normals 2020: U.S. Monthly Climate Normals (1991-2020). ncei.noaa.gov/products/land-based-station/us-climate-normals.
- NOAA National Centers for Environmental Information: Storm Events Database. ncei.noaa.gov/stormevents.
- NOAA National Weather Service: Local Storm Reports and daily climate reports (CLI), via api.weather.gov and the Iowa Environmental Mesonet.
- Iowa Environmental Mesonet, Iowa State University: Local Storm Report and NWS text product archives. mesonet.agron.iastate.edu.
- NOAA Space Weather Prediction Center: planetary K-index and OVATION aurora products. swpc.noaa.gov.
What we add
We compile the raw data into state and city totals, compute season-to-date figures, rank them, and add timestamps. The compilation and presentation are our work; the underlying numbers come from the original sources.
Names and endorsement
We name NOAA, the National Weather Service, the Space Weather Prediction Center, the National Centers for Environmental Information, and the Iowa Environmental Mesonet solely to credit the source of each figure. This does not imply endorsement by or affiliation with any of them, and we do not use their logos.
Reuse and errors
If you reuse our numbers, cite the page URL and the original source. To report an error, use the contact page. A snapshot is all an "as of" time represents: the source feeds behind it can run late, be revised, or go down.