The radio broadcast states that it is 27°F, or 3°C. (Clinton County is very close to Quebec so they would give both as a courtesy). However, 0°C=32°F so 27°F is -3°C.
The Cadillac in front of the ice cream shop has a front license plate. Quebec does not have front license plates.
When Tilly storms out of the War of 1812 Museum and walks around Plattsburgh, she cuts through Trinity Park. In the background, you can see a blue and yellow historical marker...that marker was erected by the City of Plattsburgh in the Summer/Fall of 2017, more than two years after the events of the series.