What to wear in London in July? What is the temperature like? What's the climate like?

July is the hottest season in London. However, the lowest temperature is around 15-20 degrees, and the highest temperature is around 25-30 degrees. I feel sultry occasionally. Days above 30 degrees are short, because the climate of the British Isles is affected by the Atlantic warm current and the Nordic airflow, and it often rains. Once it rains, the temperature drops obviously. So don't leave the umbrella. Short sleeves and long sleeves are ok, but when the evening comes, the coat must be on the upper body.