About the data

How we know

forty°seventy replays past storms: the radar, the warnings, the storm reports and the storm's track, with the power outages, ground stops and company filings that came with them. The name is the benchmark at 40°N 70°W, southeast of Nantucket, that forecasters measure a nor'easter's track against.

Every connection shows its work

Links are rule-based facts. A connection joins two records when a fixed rule matches, such as a ground stop that began while a warning covering that airport was in effect. Open any connection to see the rule and the exact evidence. It shows that two things overlapped in place and time.

Rules you can read

Every connection comes from a rule you can read, applied to public records. You can check our work.

A look back at past events

This is a replay of past events. For current warnings and conditions, go to weather.gov and follow your local officials.

Points and areas

Warnings and storm reports are marked as the points and areas they covered. Use a replay to review how a past event unfolded.

Power outages: what the counts are

The counts are customers (utility accounts), not people. Oak Ridge National Laboratory's EAGLE-I gathers them every 15 minutes from utilities' public outage maps.
Not every utility is covered, and coverage varies by state and year, so a county can show fewer customers out than it had.
A county's share is of ORNL's modelled customers for that county. Where more customers are out than the model counts, or there is no modelled count, the map hatches the county as “share unknown” and gives the count alone.
EAGLE-I lists only counties with customers out, so a county missing from a run counts as none out: a gap in a utility's feed can look like power coming back.
For a hurricane, a county's count starts when the storm's center first comes within 500 km of it, less any customers already out just before then, so outages from other storms in its long window aren't counted. Its restoration afterwards still is.
County shapes are the Census Bureau's 2021 boundaries, which use the same county codes as EAGLE-I.

Credits

Iowa Environmental Mesonet: the archive the radar mosaics, warning polygons and local storm reports come from (Iowa State University).
NOAA/NSSL Multi-Radar/Multi-Sensor (MRMS): the radar mosaic (SeamlessHSR).
NOAA National Weather Service: warnings and local storm reports.
NOAA Storm Prediction Center: tornado and severe thunderstorm watches.
NOAA National Hurricane Center: advisories, the forecast cone and the best track.
FAA Air Traffic Control System Command Center: airport programs (ground stops and ground delay programs).
SEC EDGAR: 8-K filings.
NOAA Weather Prediction Center: a winter storm's surface-low track and central pressure, from its coded surface bulletins (via the Iowa Environmental Mesonet).
MRMS precipitation type: which radar echoes are snow, from MRMS's precipitation flag (via the Iowa Environmental Mesonet).
NOAA National Operational Hydrologic Remote Sensing Center (NOHRSC): the snowfall totals (its 72-hour snowfall analysis; for a longer storm, with its 24-hour analysis before it).
NOAA NCEI Northeast Snowfall Impact Scale (NESIS): a winter storm's rank and category.
Oak Ridge National Laboratory, EAGLE-I: customers out of power by county every 15 minutes, gathered from utilities' public outage maps (CC BY 4.0).
U.S. Census Bureau: the county boundaries (cartographic boundary files, 2021).
Protomaps: the basemap tiles and style.

Crediting these agencies and projects doesn't imply that any of them endorses this site.