What type of air mass contributes to the hot and humid summer weather in Midwestern united States?

The hot and humid summer weather in Midwestern United States is primarily caused by the influx of warm, moist air masses from the Gulf of Mexico. These air masses are often referred to as "Gulf air masses" or "tropical air masses."

The Gulf of Mexico, located to the south of the Midwestern region, is a warm body of water that acts as a heat source. During summer, the warm waters of the Gulf generate warm and humid air through evaporation. This air is then carried northward by prevailing wind patterns, bringing it into the Midwestern region.

As the Gulf air moves over the Midwest, it brings high levels of moisture and heat. The high humidity levels prevent efficient evaporation of sweat from the skin, making the already warm weather feel even hotter. The combination of high temperature and humidity creates an uncomfortable, oppressive, and sultry weather condition often referred to as "muggy" or "sticky."

The summer weather in the Midwest is also characterized by frequent thunderstorms, which are also influenced by the presence of Gulf air masses. The warm and moist air from the Gulf of Mexico provides the necessary ingredients for the formation of thunderstorms, including moisture, instability, and lifting mechanisms. As a result, the Midwestern region experiences a higher frequency of thunderstorms during summer months.