Legend
Ranked derechos (40)
Measured gust, SPC archive (718)
Estimated gust ≥75 mph, SPC archive (826)
2026 measured gust, preliminary (205)
2026 estimated gust, preliminary (41)
Archive measured gust ≥100 mph (11)
Report outline, derived (29)
SPC archive, not drawn above: measured (under 58 mph, or a derecho shown as an outline only)
… estimated (under 75 mph, or outline-only derecho)
… damage report with no wind speed (common before 1996). Survey-sourced reports stay off: they are not gusts
Outside SPC's archive: measured gust (SPC flag, 2006 on; NWS LSR 2026)
… estimated gust
… not flagged measured/estimated (SPC flags them only from 2006)
… damage report, no speed. SPC has not assigned these reports to the derecho: every report in a stated window and set of states (see popups)
NWS severe thunderstorm warning as issued (ALERT, not a measured wind; NWS via IEM)
NWS severe thunderstorm warning as issued (ALERT, not a measured wind; NWS via IEM)
NWS severe thunderstorm warning as issued (ALERT, not a measured wind; NWS via IEM)
NWS severe thunderstorm warning as issued (ALERT). IEM's warning archive starts in 2002 (none for 1969–2000 derechos); before Oct 2007 NWS warned whole counties, drawn as the county outlines
SPC severe thunderstorm watch as issued (ALERT, forecast; thicker = PDS)
SPC tornado watch as issued (ALERT, forecast)
SPC mesoscale discussion, severe storms only (winter and rain discussions left out)
SPC severe thunderstorm watch as issued (ALERT, forecast; thicker = PDS)
SPC tornado watch as issued (ALERT, forecast)
SPC mesoscale discussion, severe storms only (winter and rain discussions left out)
SPC severe thunderstorm watch as issued (ALERT, forecast; thicker = PDS)
SPC tornado watch as issued (ALERT, forecast)
SPC mesoscale discussion, severe storms only (winter and rain discussions left out)
SPC severe thunderstorm watch as issued (ALERT, forecast; thicker = PDS)
SPC tornado watch as issued (ALERT, forecast)
SPC mesoscale discussion, severe storms only (winter and rain discussions left out). IEM archives: watches from 1997, discussions from 2002
NWS damage-survey point not EF-rated (2,335): straight-line wind (TSTM/Wind, 2,319) or no rating given (16); wind inferred from damage: an ESTIMATE, not a gust
NWS damage-survey point rated EF0–EF5 or EFU, i.e. a tornado (2,888), inside the outline and time window; it may be a separate storm. NWS Damage Assessment Toolkit, only where offices logged surveys
Blue = an instrument reading (official or private station); orange = an observer's estimate (measured gusts draw on top). Where a report's own text contradicts the archive's code or value, the dot follows the text and its popup says so. NWS damage-survey wind estimates are not gusts: they appear only in the optional damage-survey layer. Red outlines are drawn 20 km around every wind report SPC assigns to each derecho — derived, not surveyed. 2026 reports are preliminary. Click any dot. As of 2026-10-09. Optional layers (off at load), with the first derecho each covers: radar frames (1995), SPC watches (1997), NWS warnings and SPC discussions (2003), NWS damage-survey points where logged (2011), other wind reports (1969). SPC's archive publishes reports, not swath outlines, so no official swath is drawn.
Radar reflectivity (dBZ) — Aug 10, 2020, 17:30 UTC / 12:30 CDT
25–35 dBZ
35–45
45–50
50–55
55+ dBZ
NWS NEXRAD national base-reflectivity composite (N0Q), mosaicked and archived by the Iowa Environmental Mesonet; one frame, Aug 10, 2020 17:30 UTC (12:30 CDT). One colour scale on every radar layer of this map (25–35, 35–45, 45–50, 50–55, 55+ dBZ). Pixels below 25 dBZ are transparent (the same cut-off on every radar layer). Shows the storm, not the wind.
Radar reflectivity (dBZ) — Aug 11, 2026, 15:50 UTC / 10:50 CDT
25–35 dBZ
35–45
45–50
50–55
55+ dBZ
NWS NEXRAD national base-reflectivity composite (N0Q), mosaicked and archived by the Iowa Environmental Mesonet; one frame, Aug 11, 2026 15:50 UTC (10:50 CDT). One colour scale on every radar layer of this map (25–35, 35–45, 45–50, 50–55, 55+ dBZ). Pixels below 25 dBZ are transparent (the same cut-off on every radar layer). Shows the storm, not the wind.
Radar reflectivity (OBSERVED) — Aug 10, 2020 Iowa derecho, 4 frames
25–35 dBZ
35–45
45–50
50–55
55+ dBZ
NWS NEXRAD national base-reflectivity composites (N0Q), mosaicked and archived by the Iowa Environmental Mesonet, spaced through the derecho's reports to show its progress: Aug 10, 2020 14:20 UTC (09:20 CDT); Aug 10, 2020 18:05 UTC (13:05 CDT); Aug 10, 2020 21:50 UTC (16:50 CDT / 17:50 EDT); Aug 11, 2020 01:35 UTC (Aug 10 20:35 CDT / Aug 10 21:35 EDT). Each frame is cropped to the reports within about an hour of it. One colour scale on every radar layer of this map (25–35, 35–45, 45–50, 50–55, 55+ dBZ). Pixels below 25 dBZ are transparent (the same cut-off on every radar layer). Shows the storm, not the wind.
Radar reflectivity (OBSERVED) — June 29–30, 2012 derecho, 4 frames
25–35 dBZ
35–45
45–50
50–55
55+ dBZ
NWS NEXRAD national base-reflectivity composites (N0Q), mosaicked and archived by the Iowa Environmental Mesonet, spaced through the derecho's reports to show its progress: Jun 29, 2012 18:20 UTC (13:20 CDT / 14:20 EDT); Jun 29, 2012 21:50 UTC (17:50 EDT); Jun 30, 2012 01:25 UTC (Jun 29 21:25 EDT); Jun 30, 2012 04:55 UTC (00:55 EDT). Each frame is cropped to the reports within about an hour of it. One colour scale on every radar layer of this map (25–35, 35–45, 45–50, 50–55, 55+ dBZ). Pixels below 25 dBZ are transparent (the same cut-off on every radar layer). Shows the storm, not the wind.
Radar reflectivity (OBSERVED) — May 31, 1998 derecho, 3 frames
25–35 dBZ
35–45
45–50
50–55
55+ dBZ
NWS NEXRAD national base-reflectivity composites (N0R), mosaicked and archived by the Iowa Environmental Mesonet, spaced through the derecho's reports to show its progress: May 31, 1998 02:25 UTC (May 30 21:25 CDT); May 31, 1998 09:00 UTC (04:00 CDT / 05:00 EDT); May 31, 1998 15:30 UTC (11:30 EDT). Each frame is cropped to the reports within about an hour of it. One colour scale on every radar layer of this map (25–35, 35–45, 45–50, 50–55, 55+ dBZ). Pixels below 25 dBZ are transparent (the same cut-off on every radar layer). Shows the storm, not the wind.
Radar reflectivity (OBSERVED) — 1995 'Right Turn' derecho, 2 frames
25–35 dBZ
35–45
45–50
50–55
55+ dBZ
NWS NEXRAD national base-reflectivity composites (N0R), mosaicked and archived by the Iowa Environmental Mesonet, spaced through the derecho's reports to show its progress: Jul 13, 1995 08:40 UTC (03:40 CDT); Jul 14, 1995 01:35 UTC (Jul 13 21:35 EDT). Each frame is cropped to the reports within about an hour of it. One colour scale on every radar layer of this map (25–35, 35–45, 45–50, 50–55, 55+ dBZ). Pixels below 25 dBZ are transparent (the same cut-off on every radar layer). Left out for the 'Right Turn' derecho (SPC: likely) (Jul 12–13, 1995): Jul 13, 1995 00:10 UTC (Jul 12 18:10 MDT); Jul 13, 1995 17:05 UTC (13:05 EDT) — no echoes ≥ 20 dBZ in IEM's composite over this derecho's reports at these times (1995 radar-network gaps). Shows the storm, not the wind.
Radar reflectivity (OBSERVED) — 1999 Boundary Waters derecho, 4 frames
25–35 dBZ
35–45
45–50
50–55
55+ dBZ
NWS NEXRAD national base-reflectivity composites (N0R), mosaicked and archived by the Iowa Environmental Mesonet, spaced through the derecho's reports to show its progress: Jul 4, 1999 13:55 UTC (08:55 CDT); Jul 4, 1999 20:00 UTC (15:00 CDT); Jul 5, 1999 02:10 UTC (Jul 4 21:10 CDT); Jul 5, 1999 08:15 UTC (04:15 EDT). Each frame is cropped to the reports within about an hour of it. One colour scale on every radar layer of this map (25–35, 35–45, 45–50, 50–55, 55+ dBZ). Pixels below 25 dBZ are transparent (the same cut-off on every radar layer). Shows the storm, not the wind.
Radar reflectivity (OBSERVED) — June 10, 2026 derecho, 3 frames
25–35 dBZ
35–45
45–50
50–55
55+ dBZ
NWS NEXRAD national base-reflectivity composites (N0Q), mosaicked and archived by the Iowa Environmental Mesonet, spaced through the derecho's reports to show its progress: Jun 10, 2026 16:55 UTC (11:55 CDT); Jun 10, 2026 21:55 UTC (16:55 CDT / 17:55 EDT); Jun 11, 2026 02:55 UTC (Jun 10 21:55 CDT). Each frame is cropped to the reports within about an hour of it. One colour scale on every radar layer of this map (25–35, 35–45, 45–50, 50–55, 55+ dBZ). Pixels below 25 dBZ are transparent (the same cut-off on every radar layer). Shows the storm, not the wind.
Radar reflectivity (OBSERVED) — Aug 11, 2026 derecho, 4 frames
25–35 dBZ
35–45
45–50
50–55
55+ dBZ
NWS NEXRAD national base-reflectivity composites (N0Q), mosaicked and archived by the Iowa Environmental Mesonet, spaced through the derecho's reports to show its progress: Aug 11, 2026 12:05 UTC (07:05 CDT / 08:05 EDT); Aug 11, 2026 15:40 UTC (10:40 CDT / 11:40 EDT); Aug 11, 2026 19:15 UTC (14:15 CDT / 15:15 EDT); Aug 11, 2026 22:55 UTC (18:55 EDT). Each frame is cropped to the reports within about an hour of it. One colour scale on every radar layer of this map (25–35, 35–45, 45–50, 50–55, 55+ dBZ). Pixels below 25 dBZ are transparent (the same cut-off on every radar layer). Shows the storm, not the wind.
Radar reflectivity (OBSERVED) — 27 derechos, one frame each
25–35 dBZ
35–45
45–50
50–55
55+ dBZ
NWS NEXRAD national base-reflectivity composites (N0R before Nov 2010, N0Q after), Iowa Environmental Mesonet. Each frame is at the derecho's strongest measured report (otherwise the middle of its reports), cropped to the reports within about an hour. One colour scale on every radar layer of this map (25–35, 35–45, 45–50, 50–55, 55+ dBZ). Pixels below 25 dBZ are transparent (the same cut-off on every radar layer). Composites start in 1995: none for 1969, 1980, 1986 or 1993. Left out for the 'Ontario–Adirondacks' derecho (SPC: likely) (Jul 14–15, 1995): Jul 15, 1995 01:15 UTC (Jul 14 21:15 EDT) — no echoes ≥ 20 dBZ in IEM's composite over this derecho's reports at these times (1995 radar-network gaps). Each frame's UTC and local time is in that derecho's marker popup.
