If bad weather is associated with low pressure systems?

Question

Why does my barometer sometimes increase before a thunderstorm? Could it be brken because it's a few years old.

Answer 1

time for a new one, it should drop with the approach of a storm then rise when it passes

Answer 2

Thunderstorms carry a lot of precipitation with them. Due to that, there is a lot cooling going on within them. Cold air has greater pressure and weight, which sinks to the ground, and causes the barometer to detect a rise in pressure. While pressure commonly decreases ahead of a thunderstorm, sometimes this effect occurs.

There is also the possibility the barometer may need calibration. Plus there are variations between mercury and aneroid barometers.