Herewith the temperatures of the cellar and brew in this hot weather.  The kit says that the temperature should be 16-20°C.  In the days before I started it the mean temperature of the cellar was 16°C so I chose 17°C, since lower temperature gives more flavour.  The Sun then came out, and the cellar temperature slowly climbed (red line).  The variation in the cellar temperature is either the freezer switching on and off or the fan that keeps the humidity down.

You can see that the brew, which started at house room temperature, cooling down then the fermentation kicking off and the brew temperature rising again because of the respiration.  It appears to be levelling off now, and I am hoping for a cool spell.

Brew fridge next?