What is the reason for the low voltage at home in hot weather?

Household appliances are connected in parallel. The more appliances, the smaller the parallel resistance. Because the resistance in the circuit is unchanged except for the electrical appliances, the total resistance decreases, the circuit current increases, and the voltage distributed to the electrical appliances is smaller. Because the use of household appliances increases in hot days, the resistance will decrease, so the voltage of household circuits will be too low.