I know weathers sounds like a very boring topic but I assure you it isn’t, especially here in Japan.
Because Tokyo is built with basically 100% concrete, summer is extremely humid. More than it should be. The heat builds up on the walls of all the buildings around you and all the hot air stays there so walking outside is super hot. The car exhaust is areas like Shibuya or Shinagawa can largely impact heat in Tokyo. It gets hotter and hotter by the second. Temperature difference between the outside and in stores are massively different so carrying around a jumper will help. Restaurants can be the coldest places at times.
Spring time is relatively peaceful, temperature is constant and it stays sunny for days sometimes weeks at a time. Afterwards comes a period called Tsuyu (梅雨) where it just rains and rains. Its usually during June to early July. Humidity skyrockets and many people get sick because of the drastic changes in the weather. In Autumn the Kouyou (紅葉) is super pretty so thats worth seeing and the weather is very cool and cloudy so its worth a visit! Winter is just very cold and dry. It can be sunny and it can be cloudy but cool most of the time. If you’re lucky you might have a snow day!
Its extremely humid right now and whenever I go outside its all I can think about because its just THAT HOT!! Japan’s weather in general is a little unstable and likes to change out of the blue. Its quite temperate so the weather can be quite exaggerated. Maybe its my white genes kicking in. My mother always complains about the heat but tells me I should be ok because Im half Japanese but it doesn’t feel like it!
If you’re planning a visit I would recommend checking the weather before hand! Usually early summer, mid fall and spring in general is the best for Tokyo.