Hot weather will increase the sales of refrigerators. From an economic point of view, what are the factors that lead to the increase in sales?

The increase of income makes the consumer's budget line move to the right and cross a higher indifference curve, thus maximizing consumption and leading to an increase in sales. The reason why prices drop and sales increase is the demand theorem. Demand and price change in opposite directions, and the decline in price leads to an increase in demand, thus increasing sales.