we plan to visit Shanghai and Beijing in June, is it a good weather during this time?

In my opinion, it is not good travel season in both places.

However, it is during June that Beijing and Shanghai welcome the travel season. The average temperature would be about 25C. So summer clothes are necessary. There is different temperature gap between the daytime and night, so you may also need to take along long-sleeved shirt or a light coat. It would rain from time to time and thunderstorm may also happen. Umbralla or rainy gear is suggested if you travel then.