Right now
The most recent data we hold from NOAA arrived 22 minutes ago, and this point is not in it. We record detections, not passes: an absence is not proof that nothing is there.
Nothing else has been detected within 20 km in the last 24 hours.
This alert expired on 27 July 2026 at 18:15 UTC. It is kept here as a record.
No stronger detection stands among the 239 recorded within 20 km of this point since 10 March 2026 — 18 others scored the same. Another comparable one was recorded here earlier the same day. 3 more were recorded here in the fortnight before it.
What the source measured
NOAA reported: Tornado Warning issued July 27 at 12:18PM CDT until July 27 at 1:15PM CDT by NWS Chicago IL
Urban PEI: 8,382,812 within a heuristic 50 km radius; not unique people.
Nearby, since 10 March 2026
- July 27, 2026 · score 76 · 1.6 km
- July 4, 2026 · score 52 · 3.6 km
- July 4, 2026 · score 52 · 4.2 km
How we know
One source: NOAA. Not yet confirmed by a second, independent source.
Our own score for this event is 76 out of 100.
This is our versioned heuristic index, not source severity or a calibrated probability. Urban PEI does not count unique people.
Computed under scoring rules v1. Rows carrying other versions were judged by different rules and are not directly comparable.
Event Data
| Type | Severe Weather |
| Severity | Critical |
| Calamity Score (ours) | 76 / 100 |
| Legacy data-support index | 0.81/1 |
| Coordinates | 41.6867, -87.9339 |
| Nearest City | Lemont (6 km) |
| Urban exposure index (PEI) | 8.4M within 50 km |
| Impact Tier | catastrophic |
| Timestamp | 2026-07-27T17:18:00.000Z |
| Source | https://api.weather.gov/alerts/merged_Tornado Warning_noaa_urn:oid:2.49.0.1.840.0.927f629cced157bb0e65e7b20287a9ef |
Physical priority index · v1. Heuristic priority, not calibrated probability, predictive accuracy or damage. The legacy data-support index combines assigned source support and field availability. Urban PEI is distance-weighted and does not count unique people; zero does not establish that nobody is present. Model cards.
Source and revision timeline
Source: noaa. Occurrence: 2026-07-27T17:18:00.000Z.
First archived: 2026-07-27T17:20:36.273Z. Material modification: not recorded.
Retained revisions are prospective; earlier versions may be unavailable. No revision entry does not prove that a record never changed.
Score Breakdown
Technical Details
| Event | Tornado Warning |
| Urgency | Immediate |
| Certainty | Observed |
| AreaDesc | Cook, IL; DuPage, IL; Will, IL; DuPage, IL |
| Headline | Tornado Warning issued July 27 at 12:18PM CDT until July 27 at 1:15PM CDT by NWS Chicago IL |
| Expires | 2026-07-27T13:15:00-05:00 |
| SenderName | NWS Chicago IL |
| HasExactCoords | true |
| MergedCount | 2 |
| MergedIds | ["noaa_urn:oid:2.49.0.1.840.0.927f629cced157bb0e65e7b20287a9ef16c35f3a.001.1","noaa_urn:oid:2.49.0.1.840.0.712947e6929d9c2543bc450fe223d6d59caaf874.001.1"] |
Safety Information
If a tornado warning is issued: go to a basement or an interior room on the lowest floor, away from windows. A vehicle and a mobile home are not shelter. Cover your head and neck. Wait for the official all-clear before going outside, and watch for downed power lines and gas leaks afterwards.
Series begins 8 March 2026. Comparisons refer to that period only. Collection gap: 14-26 August 2026.
This data is aggregated algorithmically from scientific sources. Not a replacement for official emergency warnings.
Review the area, threshold and delivery channel in your account.
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