When is the air pressure high in winter and summer?

Of course, the pressure is high in winter.

First of all, it should be clear that air pressure refers to the atmospheric pressure formed near the ground, not the troposphere.

In winter, the temperature is low, the air density is high, the gas contracts, the atmosphere flows downwards, and the molecules in the atmosphere gather near the ground.

In summer, due to high temperature, gas expansion and upwelling, there are fewer molecules near the ground, so the density is smaller.