A 1000 Megaton would kill 878,000 people in and around Edmonton if one fell according to Nuclear Secrecy.
It’s very rare that the USSR would send a 1000 Megaton bomb to Canada, they are the only ones that one, in today’s age even if world war three broke out, it would still be rare to see a 1000 megaton bomb being launched.
But how would it affect the area? Here’s some stats:
Radiation radius (500 rem): 6.99 km (153 km²)
500 rem radiation dose; without medical treatment, there can be expected between 50% and 90% mortality from acute effects alone. Dying takes between several hours and several weeks.
Fireball radius: 7.92 km (197 km²)
Maximum size of the nuclear fireball; relevance to lived effects depends on height of detonation. If it touches the ground, the amount of radioactive fallout is significantly increased.
Air blast radius (20 psi): 10.1 km (321 km²)
At 20 psi overpressure, heavily built concrete buildings are severely damaged or demolished; fatalities approach 100%. Often used as a standard benchmark for heavy damage in cities.
Air blast radius (5 psi): 21.2 km (1,420 km²)
At 5 psi overpressure, most residential buildings collapse, injuries are universal, fatalities are widespread. Often used as a standard benchmark for medium damage in cities.
Read the full stats here.