| Event Category | Disaster |
| Event Group | Natural |
| Event Subgroup | Meteorological - Hydrological |
| Event Type | Storm - Unspecified / Other |
| Place | Southern Ontario |
| Event Start Date | May 4, 2018 |
| Event End Date | May 5, 2018 |
| Comments | On May 4th, the Highway 401 corridor through southern Ontario and southern Quebec experienced a fast-moving squall line with wind gusts of over 100 km/hr. Wind speeds of 126 km/hr were recorded in Hamilton and 117 km/hr in Montreal. The windstorm caused widespread power outages, roof damage and downed trees. Over 925,000 customers across Ontario and Quebec were without power; some were without power until May 9. The windstorm caused a total of $680 million in insured losses, with at least $380 million in Ontario alone. This event is noted to be the most costly disaster in Ontario since the 2013 Toronto flood. |
| Fatalities | 3 |
| Injured / Infected | Unknown |
| Evacuated | Unknown |
| Estimated Total Cost | $680,000,000 |
| Federal DFAA Payments | Unknown |
| Provincial DFAA Payments | Unknown |
| Provincial Department Payments | Unknown |
| Municipal Costs | Unknown |
| OGD Costs | Unknown |
| Insurance Payments | $680,000,000 |
| NGO Payments | Unknown |
| Utility - People Affected | Unknown |
| Magnitude | Unknown |