The climate in Paris is typical sea climate, meaning that the summer is not the warmest, and the winter is quite mild. This information means that in the summer the temperature normally feels quite comfortable, while the winter is cold, but not too cold. The warmest months of the year is June, July and August with an average temperature of approximately 24 Celsius.
It might be useful to know that it is quite often raining in Paris, so do not forget to have an umbrella in your backpack!