The answer is likely a microclimate.
CTV Calgary Meteorologist David Spence explains that microclimates are simply changes in climate over very short distances.
“If a farm is on rolling land, you will notice that it can get colder at night in the valleys than the higher elevations,” said Spence. “In the spring or the fall this can be really important because the cold air drains into the valleys and you are more likely to get frost.”
To illustrate the point Spence says imagine an overnight low of plus four degrees Celsius.
“The air down at the surface will cool to four degrees, but then that cool air will drain into a valley and continue to cool down as it goes down.”
The veteran meteorologist says that’s why the warnings from Environment Canada indicate frost is possible in low-lying areas.
Spence says microclimates are really noticeable in situations where a field meets a forest.
“The forest will be considerably cooler than the forest and they will be just 200 yards from each other,” Spence says.
He says that is one reason why so many thunderstorms develop in the Sundre and Rocky Mountain House area, because there are two different types of land uses, with the difference in heating generating the stormy weather.