The terms 'sweltering', 'scorching' and 'burning' are synonyms for the expression 'violent heat'. These words describe intense, overwhelming heat that can cause discomfort or even be dangerous to human health. Sweltering heat suggests a suffocating, oppressive atmosphere that can be stifling to breathe in. Scorching heat implies a blistering, searing level of temperature that can cause actual burns on the skin. Burning heat suggests a level of heat that is so intense that it feels like the body is being incinerated. All of these words are used to convey the severity and intensity of extreme levels of heat.