Low-pressure systems bring wind, rain and thunderstorms. Warm air moves upward from the surface to cause a low-pressure system. As the air rises, its temperature decreases, water vapor occurs as a reaction and clouds form, which brings weather indicative of the system.
The introduction of a low-pressure system is usually the result of a mix of warm and cold fronts in an area from which the system receives the necessary moisture to produce rain and storms. In the northern hemisphere, the area east of a low-pressure system experiences a warmer temperature, while temperatures are colder to the west. Weather under low pressure is unstable in comparison to systems in high pressure.