Valefor,
nice to see you after a long time. How are you doing?
By the way, I realized that we use two different temperature scales - Fahrenheits - which is used in the USA and Celsius - used in Poland. I am not sure which scale is used by Brits. Anyways - 90 F means above 30 C and the temperatures 15-20 C are in 60-es of Fahrenheits.
Here is the converter:
http://www.albireo.ch/temperatureconverter/I got used to Fahrenheits because its scale is more expanded and it is easy to judge that for instance the temperatures are in the 40-es, 60-es or 90-es, whereas the differences of temperatures from 20-30 C is much bigger and the information that the temperatures (in C) are in 20-es is much more "rough".