Weather Manipulations

Just checked my thermometer outside: Minus 4 Celsius
My computer which takes the weather data from a local station shows minus 2 Celsius.
I have noticed that most of the time my thermometer shows 1-2 degrees less than the local weather station.
I will use the local weather station anyway regardless of them showing 1-2 degrees higher temperatures and compare with another station in the same town.
( could be the same station that puts it's data on the Internet )
Stations record the temperature automatically. One thing I can not do.
So I will compare the Internet stations data with the screen captures I took from my desktop showing the temperatures of the local station.
I will concentrate on the minimum temperature.
The station is:
http://www.accuweather.com/en/fi/turku/134768/march-weather/134768
Lowest temperatures in Turku March 2013
March 3 = minus 16 station shows minus 15 = cheating 1 degree
March 7 = minus 15 station shows minus 12 = cheating 3 degree
March 9 = minus 19 station shows minus 15 = cheating 4 degrees
March 10 = minus 23 station shows minus 20 = cheating 3 degrees
March 15 = minus 21 station shows minus 19 = cheating 2 degrees
March 16 = minus 22 station shows minus 16 = cheating 4 degrees
March 24 = minus 12 station shows minus 09 = cheating 3 degrees
March 25 = minus 13 station shows minus 11 = cheating 2 degrees
March 26 = minus 11 station shows minus 05 = cheating 2 degrees
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March 3AM and the
dropped most likely even more ( -15)

March 7PM (-12)
March9
March9AM (-15)
March10
March10AM(-20)

March15AM (-19)

March 16AM (-16)

March24AM (-9)

March25AM (-11)

March26AM (-9)
They just updated their webpage
The logic is simple. They can record the lowest temperature while I only can take random shots.
I compare my lowest temperature random shots with their records. Why do they show on so many occasions higher temperatures?
Hide the decline comes to my mind. Hide the minimum temperatures and voila! Global Warming.
Update:
Just did a double checking.
My thermometer ( 3 inches from my outside window ) showed -2.5C
The local weather station to which my computer connects shows 0C
My infrared thermometer showd a outside temperature of  -4,4C
I live 10km from the coast and 5 km from the city center.
The weather station is 5km from the coast and very near the center ( Turku railway station )