What Is a Severe Thunderstorm Watch?
A Severe Thunderstorm Watch means conditions are favourable for the development of severe thunderstorms in or near the watch area. While severe weather has not yet been confirmed, storms capable of producing damaging winds, large hail, heavy rainfall, or tornadoes may develop.
A watch is issued to give people advance notice so they can monitor weather conditions and be prepared if storms strengthen.
What Is the Difference Between a Severe Thunderstorm Watch and a Severe Thunderstorm Warning?
A Severe Thunderstorm Watch means severe thunderstorms are possible.
A Severe Thunderstorm Warning means a severe thunderstorm has been detected by radar or reported by trained weather observers and is occurring or expected imminently.
In short:
- Watch: Be prepared.
- Warning: Take action.
What Conditions Can Trigger a Severe Thunderstorm Watch?
Environment and Climate Change Canada may issue a Severe Thunderstorm Watch when atmospheric conditions are favourable for severe storms.
These conditions often include:
- Warm, humid air
- An approaching cold front
- Strong instability in the atmosphere
- Wind shear that can organize thunderstorms
Not every watch results in severe weather, but the potential is high enough to warrant close attention.
What Hazards Can Severe Thunderstorms Produce?
Severe thunderstorms can produce one or more dangerous hazards, including:
- Damaging wind gusts
- Large hail
- Frequent lightning
- Torrential rainfall
- Flash flooding
- Isolated tornadoes
Storms can develop rapidly, especially during the spring and summer months.
What Should You Do During a Severe Thunderstorm Watch?
When a Severe Thunderstorm Watch is issued:
- Monitor the latest weather updates.
- Have multiple ways to receive warnings.
- Secure outdoor furniture and loose objects.
- Delay outdoor activities if storms are approaching.
- Prepare to move indoors quickly if a warning is issued.
- Charge electronic devices in case of power outages.
A watch gives you time to prepare before severe weather develops.
How Long Does a Severe Thunderstorm Watch Last?
A Severe Thunderstorm Watch remains in effect until:
- The threat of severe thunderstorms has ended.
- It is upgraded to a Severe Thunderstorm Warning.
- Weather conditions become less favourable for severe storm development.
Forecasts are updated regularly as storms develop and move.
