I've had an interest in personality across culture in our country for years, what a cool thread. I lived in Edmonton for 14 years and practiced psychology there for 3, and lived in Hamilton for 17 while practicing for 5 years.
The best academic explanation I've found is that being introverted is correlated with altitude. The higher you go, the more introverted the population. It's not perfect and it by no means explains all the differences, but absolutely makes sense to me.
Central BC (Kelowna) and coastal BC felt similar to home near Lake Ontario. The culture, the outgoing social nature of people, lefty values, even little things like wineries and roadside fruit stands similar to the Niagara region.
As other people have mentioned, water brings people together. At the beach, you constantly meet new people against a backdrop of activities like volleyball, boating, swimming etc.
The temperate climate means people are outside more, and there are more opportunities for social engagement.
Alberta was very jarring for me. One of the main differences you notice immediately coming from the GTA is no one is outside. The city layout is not walkable. People are not sitting on porches, I never saw anyone BBQ out front, etc.
People from "warmer" cultures, even foreign ones like Brazil, had similar complaints. It's hard to make friends, people don't hang out as much, they aren't as vulnerable in terms of being open about what's happening in their life and what they think/feel.
I think a lot of it has to do with the transient nature of the population. It's not a collection of deeply rooted and established communities, but a destination for work.
If it sounds like a negative take on Alberta, it's because it is one. This isn't to say Alberta is a negative place, but as someone accustomed to a different culture it was uncomfortable.
I met my wife in Edmonton, and she had similar complaints about Ontario. People down here talk... a LOT. I didn't notice it until we moved back here after living out west for years.
People seem to be much more emotionally sensitive. A lot more people sue, billboards everywhere for lawyers.. especially injury law. Men gossip with each other and act in more traditionally feminine ways.
If I had to summarize psychologically, people in coastal (including major lakes) environments tend to be more extraverted and emotionally preoccupied. People in rural areas are more emotionally avoidant.
Preoccupied means people feel more and are more agitated by emotions. Feelings play a bigger role in governing the day to day experiences of a person. People like this vent about emotions, talk to friends, become upset easier, seek connection with others and escalate emotionally when faced with difficulties in relationships.
Avoidant means emotionally suppressing and compartmentalising. People like this are more likely to bottle feelings, disconnect from others, drink/work excessively to cope, and shut down and withdraw when faced with difficulties in personal relationships.