I stayed late August, and maximum temperature was 22-25degC, except one day (29degC). The room was not equipped with air conditioner, but no problem.
Not gorgeous, but it's comfortable to stay this hotel. There are not large but enough space, shower booth, desk, bed, closet, middle size TV, etc. Continental breakfast: bread, ham, cheese, boiled egg, tomato, cucumber, cereals, coffee, etc.
It is located in front of Hamburg hauptbahnhof, where you can find a supermarket, grocery shops, and food shops. It's convenient.