You’ve probably noticed that thunderstorms are not uncommon in late afternoon after a particularly hot summer day, especially when the air is sticky with humidity. Thunderstorms rely on warmth and humidity to develop, so the spring and summer months provide all the ingredients they need. Moisture and warm air rises into the atmosphere, forming cumulus clouds as they reach the cooler air of the upper atmosphere. The rays of the sun are more direct, producing more heat, and the days are longer, allowing more heat to collect, and subsequently rise into the upper atmosphere. While thunderstorms can and do happen in every season of the year, conditions are more likely to produce them in the warmer months.
Most summer storms are fairly short-lived. The cumulus, white puffy cloud, becomes a cumulonimbus cloud, the dark, threatening signs that preceded the storm. A downdraft begins in the cloud, producing rain, thunder and some lightening, and the storm is over. However, other storms, especially in open areas and areas that are high in humidity, will become mesoscale convective systems that can cover over 100 miles. These produce high winds, heavy rain, and occasionally, tornadoes. These violent and deadly storms are most prevalent in the spring, presumably when cold fronts and warm air are most likely to collide, causing super cell storms. The increase in the warm air updrafts cause activity in the atmosphere that causes rotation, and the increasing rotation spins faster and faster, forming a cylinder that becomes the tornado. Dry lines, or cold fronts will sometimes begin in the west and push warm moist toward the east, accumulating more and more moisture, forming larger and larger storms. As the warm moist air from the heated earth rises and the humidity forms clouds, the water droplets collide with other moisture in the air. Electrons are knocked off the rising moisture, which created a charge separation. The negative charges of at the bottom of the clouds, and the positive charge at the top of the cloud, produces an electric field, and the strength of the field determines the intensity of the storm. The conductive path that the electric field takes is the earth’s surface, creating lightening, and the heating and rapid cooling produce thunder.
Every season of the year has it’s drawbacks, and storms are some of the least pleasant occurrences in summer. However, storms also bring needed rain, and often relief from high temperatures.
http://www.ucar.edu/news/features/springstorms/
