Madrid is very hot in Summer with heat waves over 40°C. The concrete jungle of the city can also create a heat island effect. Escape the city and get into the altitude of the green mountains to avoid the heat.
It is also very dry. Some lakes can be emptied which makes them not as pretty as normal. But the dry summers make it perfect for cycling, as long as you plan your rides early in the mornings to escape the heat.
During the August holiday period, most Madrid residents leave the city to visit other holiday destinations. It can feel like a ghost city! There’s not much traffic as a result.
Madrid is not as touristy as other European cities and there is no distinct tourist high season. Most international tourists come for the city, not the mountain areas where cyclists like to ride.