Air temperature can indeed have an impact on the calories burned through basal metabolism, also known as basal metabolic rate (BMR). Basal metabolism refers to the energy expended by your body to maintain essential functions while at rest, such as breathing, circulation, and organ function.
When the ambient air temperature increases, such as in the range of 20-30 degrees Celsius (68-86 degrees Fahrenheit), it can have a minor effect on BMR. Higher temperatures generally lead to a slight increase in BMR due to the body's efforts to dissipate excess heat and maintain a stable core temperature.
In warmer environments, your body needs to work harder to cool down and maintain a stable body temperature through processes like sweating and vasodilation (expansion of blood vessels near the skin surface). These physiological mechanisms require energy expenditure, leading to a slightly higher BMR. However, it's important to note that the impact of temperature on BMR is relatively small compared to other factors such as body composition, age, and genetics.
It's worth mentioning that extreme temperatures, both hot and cold, can have a more significant impact on energy expenditure through additional processes like shivering or seeking shade. However, in the moderate temperature range you specified, the effect on BMR is relatively minor.
Keep in mind that physical activity, such as exercise, has a much larger impact on overall calorie expenditure than the minor fluctuations caused by temperature. So, while temperature can influence BMR to some extent, it is unlikely to be a primary factor in determining your daily caloric needs.