Sweating does not burn calories. An increase in temperature does not result in an increase in calorie burn. It results in the loss of water.
When the temperature of your body rises, your body tries to prevent this by releasing more sweat. This process is aimed at lowering your general body temperature. This process results in a loss of water weight.
The results of this process are temporary. The weight loss is reversed as soon as liquids are ingested. The weight lost does not effect your body's fat tissue.
Increased temperatures bring health risks. Dehydration, hyperthermia, heat stroke, low blood pressure, fainting, dizziness and burns are all possible results of increased temperatures.