Inconsistency with WeatherData

Normal[WeatherData[ WeatherData[ Entity["City", {"Birmingham", "Alabama", "UnitedStates"}]], "MeanTemperature", {{2019, 1, 1}, {2020, 12, 31}, "Day"}]][[All, 2]] // Length

Gives 730 which makes sense because DateObject[{2020, 12, 31}] - DateObject[{2019, 1, 1}]=730

but

Normal[WeatherData[ WeatherData[ Entity["City", {"Huntsville", "Alabama", "UnitedStates"}]], "MeanTemperature", {{2019, 1, 1}, {2020, 12, 31}, "Day"}]][[All, 2]] // Length

Gives 731, why?

Normal[WeatherData[ WeatherData[ Entity["City", {"Auburn", "Alabama", "UnitedStates"}]], "MeanTemperature", {{2019, 1, 1}, {2020, 12, 31}, "Day"}]][[All, 2]] // Length

Gives 681, why?

Normal[WeatherData[ Entity["City", {"Auburn", "Alabama", "UnitedStates"}], "MeanTemperature", {{2019, 1, 1}, {2020, 12, 31}, "Day"}]][[All, 2]] // Length Gives 731, why?

Is there a way to get consistent data i.e. 730 temperature data for each city in the US?