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The public record for one day, one state

What happened in Illinois on July 21, 2017: hail, wind and tornadoes on record

The public federal storm record holds 24 hail reports, 55 wind reports and 3 tornado reports for July 21, 2017 filed under Illinois. The largest hail measured by a person or an instrument is 1.25″. The strongest measured wind is 90 mph. The day's hail was carried by 3 independent sources.

82

Reports on record, hail, wind and tornado

24

Hail reports, all sources

1.25in

Largest hail measured on the ground

3

Independent sources carrying the hail

Where it fell

The counties the day's reports were filed under in Illinois, busiest first, as the source filed them. The size beside each is the largest hail filed there.

  1. ROCK ISLAND Not sized
    • 10 wind
  2. COOK 1.25″
    • 7 hail
    • 2 wind
  3. KANE 1.00″
    • 4 hail
    • 5 wind
  4. WHITESIDE Not sized
    • 4 wind
    • 2 tornado
  5. DU PAGE 1.25″
    • 2 hail
    • 3 wind
  6. DUPAGE 1.25″
    • 2 hail
    • 3 wind
  7. WINNEBAGO 0.25″
    • 1 hail
    • 3 wind
  8. STEPHENSON 0.25″
    • 1 hail
    • 2 wind
  9. CARROLL Not sized
    • 2 wind
  10. IROQUOIS Not sized
    • 2 wind
  11. WILL Not sized
    • 1 wind

Places in the footprint

Every place in Illinois with a hail report of the day within 10 miles of its centre, by reports. Each links to the place's own hail history; the busiest 40 are listed.

  1. Schaumburg 16 reports 1.25″
  2. Arlington Heights 16 reports 1.25″
  3. Des Plaines 16 reports 1.25″
  4. Mount Prospect 16 reports 1.25″
  5. Hanover Park 16 reports 1.25″
  6. Addison 16 reports 1.25″
  7. Glendale Heights 16 reports 1.25″
  8. Elk Grove Village 16 reports 1.25″
  9. Rolling Meadows 16 reports 1.25″
  10. Roselle 16 reports 1.25″
  11. Bloomingdale 16 reports 1.25″
  12. Bensenville 16 reports 1.25″
28 more places in the footprint
  1. Wood Dale 16 reports 1.25″
  2. Itasca 16 reports 1.25″
  3. Hoffman Estates 14 reports 1.25″
  4. Prospect Heights 14 reports 1.25″
  5. Elmhurst 13 reports 1.25″
  6. Park Ridge 13 reports 1.25″
  7. Villa Park 13 reports 1.25″
  8. Franklin Park 13 reports 1.25″
  9. Northlake 13 reports 1.25″
  10. Schiller Park 13 reports 1.25″
  11. Berkeley 13 reports 1.25″
  12. Carol Stream 12 reports 1.25″
  13. River Grove 12 reports 1.25″
  14. Palatine 11 reports 1.25″
  15. Streamwood 10 reports 1.25″
  16. Niles 10 reports 1.25″
  17. Norridge 10 reports 1.25″
  18. Harwood Heights 10 reports 1.25″
  19. Inverness 10 reports 1.25″
  20. Lombard 9 reports 1.25″
  21. Melrose Park 9 reports 1.25″
  22. Glenview 7 reports 1.25″
  23. Wheeling 7 reports 1.25″
  24. Elgin 6 reports 1.00″
  25. Bartlett 6 reports 1.25″
  26. Carpentersville 6 reports 1.00″
  27. Algonquin 6 reports 1.00″
  28. Lake in the Hills 6 reports 1.00″

By kind of evidence

A day carried by a ground observation, a radar detection and a warning is attested three independent ways. A day carried by one kind from one source is one report. Each report below keeps its own source.

By kind of evidence: the kinds of evidence on record for the day, the number of independent sources of each, and the reports each contributed.
Evidence Sources Reports
Ground observation ×3 82

Largest hail reports on the day

Measured Detected, not measured

Largest hail reports on the day: time, hail size, evidence and where the report was taken.
Time (UTC) Size Evidence County
22:00 1.25″ Ground observation COOK
21:49 1.25″ Ground observation COOK
21:55 1.25″ Ground observation DU PAGE
21:55 1.25″ Ground observation Not stated
21:49 1.25″ Ground observation Not stated
22:00 1.25″ Ground observation Not stated
21:49 1.25″ Ground observation COOK
22:00 1.25″ Ground observation COOK

Neighbouring days

The nearest days either side with anything on record in Illinois, the same date in other years, and the hail history the day belongs to.

Previous day with records
July 20, 2017
Next day with records
July 22, 2017
This day in other years
Hail history and data
The next step

The day is on record. The report is what reached the roof.

Everything above is the record for the day: enough to know there was a storm, where it was reported and how large. None of it says what reached one roof.

Run the address and the same archive is searched at the property: each report's distance and bearing from the roof, the measured size, the sources by name, and the federal record each figure came from, in a document that states its own method. About a minute.

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The next day of record

A storm day that enters the record in Illinois can be sent within hours of its page: the date, how many independent sources carried it, and the link to the day.

Storm alerts

The next day like this one, sent for Illinois.

A territory is a set of states, or up to 5 places with 30 miles around each. An alert names the largest hail measured and the largest detected, kept apart; a weekly digest lists the last 7 days every Monday. Nothing is sent until a confirmation link is opened.

Subscribe to alerts

How this page is made

What counted
Every hail report in the archive filed on July 21, 2017 under Illinois, with wind and tornado reports counted beside it and the places ranked by the hail reports within 10 miles of each centre. A hail day is a calendar date with at least one report: four sources describing one storm are one afternoon of hail, not four.
Measured and detected
A report from a person or an instrument is measured. A radar-derived size is a detection and is marked as one, here and in every document we issue. The two are never added together.
Severe
A day counts as severe when its largest report reached 1.00″, the National Weather Service criterion. Smaller hail is still on the record, and still on this page.
What this is not
Reports are counted as the sources filed them, so a storm four sources describe is four reports on this page and one afternoon of hail on a place page. This page is the record for a day; it is not a report on any property, and it states no opinion about one.
Terms used on this page
Storm day, independent source, measured and detected: each term this page uses is defined in the glossary as the report prints it.
The record
Searched from 1996 to today. Compiled 24 August 2026 and rebuilt daily as the archive deepens. Records are reproduced as the federal sources published them. The coverage page states what the record holds, by kind and by year.

About this record

Everything here is reproduced from public federal and volunteer weather records, as the agencies and observer networks that publish them released it. Titan Weather compiles the record; it does not observe the weather, and it is not affiliated with any source it cites.

No archive holds everything. Storms cross places where nobody is standing, instruments and spotters cover some areas better than others, sources revise their records, and recent reports can take weeks to arrive and settle. Where this page shows nothing, nothing was found in the sources searched, within the period and area it states. That is not a finding that no weather occurred.

These pages describe the public record near a place or on a date. They do not establish what reached any particular property, and nothing here is insurance, legal or engineering advice.

Settled or provisional
Settled. The last national segment covering this day settled on August 24, 2026, and the figures above are drawn from the settled record.