After we have a cold night in summer (like 50 - 60 degrees at night when it is in the 80's during daytime), or in winter when the temps go down low at night, I notice in the morning after showering or otherwise using the water heavily there is a lingering sewer odor outside our house. We have a septic system that has been inspected recently and is in good working order and we do not abuse it at all... we even have a lint filter on the laundry drain. Why does this odor occur after cold nights... it is not noticeable any other time it seems.

Call a plumber... may be nothing and common or a very expensive leak! Most especially if you are on a septic system. Ikes

Usually, warm sewer gases cool down rapidly in cold weather and hang around ground instead of raising - especially on windless days...