Low coolant warning, common?

The last few days its been pretty cold over here and I have noticed my Low Coolant Warning light comes on in the inst. cluster, but when i drive the car for a while then restart the car it shuts off, and then come back on randomly the next time I start the car. From what i see my coolant is not low, unless im reading it wrong wich i doubt. Question is, is this common because of the cold or is it just me? This is my 2nd winter with the stang but i really didnt drive it when it was this cold last winter. Thanks
 
My light always comes on even during summer (i dont use the stang in winter, duh).... One gearhead i know told me it's because the coolant tank is so cheap that after a while it spills out a bit from the bottom.. so i always keep a coolant bottle in the stang.
 
FWIW...Check the pass side of the radiator for a small leak...The plastic/Alum radiators tend to leak some in the cold...mine drinks almost a 1/2 gallon a year...only in the cold mostly....the leak seems to dry up in the Summer ??? Been that way since 98 when I bought it...