The most basic change in pressure is the twice daily rise and fall in due to the heating from the sun. Each day, around 4 a.m./p.m. the pressure is at its lowest and near its peak around 10 a.m./p.m. The magnitude of the daily cycle is greatest near the equator decreasing toward the poles.

How quickly does air pressure change?

Amount of Barometric Change If barometric pressure rises or falls more than 0.18 in-Hg in less than three hours, barometric pressure is said to be changing rapidly. A change of 0.003 to 0.04 in-Hg in less than three hours indicates a slow change in barometric pressure.

What causes air pressure to fluctuate?

Air pressure fluctuations occur primarily because of changes in temperature, elevation and humidity. Regarding temperature, warm air is less dense than cool air. As air is warmed, its molecules move faster and are spaced farther apart, causing its density and consequently its air pressure to decrease.