Tires: tire pressures, winter tire pressure

Question
I need to know the difference between the tires pressures during winter and summer.

Answer
Brian,

If you mean: "What are the differences between operating pressures between summer and winter?" - there are any.  A tire's pressure should be the same.  However many people feel that they get a better traction if they use 3 to 5 psi over the placard pressure.  Perhaps I should explain the placard.

On every vehicle sold in the US, there is a sticker - commonly called the placard - which lists the original tire size and proper pressure for that size.  The placard is usually located on a door post or in the glove box.

But if you mean:  "If I inflate a tire during the summer, what will be its pressure in winter?"  Then the rule of thumb is that for every 10F decrease in temperature, there is a 1 psi drop in inflation pressure.