Our house is 8 years old. We have a septic system. Every year when the weather gets colder (30 to 40 degrees F?

Our house is 8 years old. We have a septic system. Every year when the weather gets colder (30 to 40 degrees F) we have a sewer smell in the house when we use the dishwasher, washing machine or take a shower. As long as the temperature is above 50 there is no smell. We have a bathroom in the basement, 2 and 1/2 baths on the 1st floor and a bath on the 2nd floor that is not used very often. We have the septic tank pumped out each year. Any ideas or suggestions?