Warning - Issued when severe weather is either imminent or occurring. Severe thunderstorm warnings, by their nature, will be issued less than one hour in advance. Severe thunderstorm and tornado warnings may be issued specifically for smaller warning or "sub-regions" within the regular forecast area where available.
Issued when conditions are favourable for the development of severe weather. Watches are typically issued for local-scale events in which the timing and location of occurrence remains uncertain; such as severe thunderstorms or tornadoes. A watch is normally issued several hours in advance. A watch issued for severe summer storms is typically issued up to six hours in advance.
Special Weather Statement/ Advisory - Issued in a freestyle format for weather events that are unusual, cause general inconvenience or public concern and cannot adequately be described in a public weather forecast. A Special Weather Statement may also be issued to indicate any potentially hazardous situation in the long term forecast.
Use of Home Generators
Home generators are handy for backup electricity in case of an outage, but must only be used in accordance with the manufacturer's guidelines. A back-up generator may only be connected to your home's electrical system through an approved transfer panel and switch that has been installed by a qualified electrician. Never plug a generator into a wall outlet as serious injury can result when the current produced by the home generator is fed back into the electrical lines, and transformed to a higher voltage. This can endanger the lives of utility employees working to restore the power. (getprepared.gc.ca)