28 is right on the ragged edge of turning on the warning light. Since all four tires are about the same, it is unlikely there's any problem, they just need to be aired up. Tire pressure changes with temperature, so it's a good idea to check them seasonally. I set my cold pressure to what is recommended on the sticker on the driver's door.

 

It got colder. Always need to add air if the ambient is 10 or 15 degrees cooler than when it was set. For me, it's about 2 psi for 15 degrees.

 

Air up the tires to the recommended pressures stated on the door sticker, and go drive wherever you are planning to go this holiday. Unless the light comes on within a short time, it appears you haven’t any tire issues. It will take a few miles after you air up to turn the light off.

 

The only manufacturer that I know of that gave a temp per PSI spec is Hyundai. Hyundai says 1 PSI per 12'F of temp difference. 35 in front 33 in rear. You just need to add air. It would be a good idea to check the spare too. 60 PSI there.

 

I have always followed a 1 psi loss or gain for each ten degrees of temperature change and adjust my tires to reflect expected seasonal temperatures. Southern Wisconsin winters will have long periods of temperatures in the 20s so when I checked my tires recently while it was in the 40s I added 3 psi. I feel confident the tires will be sufficiently inflated even if the temperature drops into the teens. When the days get longer and the temperatures rise again I will release some air back into the atmosphere to keep the tires from being over inflated.