Poland is a country in Central Europe with mostly temperate climate. The spring arrives slowly in March or April, bringing mainly sunny days after a period of alternating wintertime and springtime conditions. Summer, which extends from June to August, is generally less humid than winter. Showers and thunderstorms alternate with dry sunny weather that is generated when southern and eastern winds prevail. Early autumn is generally sunny and warm before a period of rainy, colder weather in November begins the transition into winter. Winter, which may last from one to three months, brings frequent snowstorms but relatively low total precipitation.
The average temperature between 15-18 September in Lodz is 14-17 °C (day) / 7-9 °C (night).
Please find below the links where you can find the average temperature in September: