The jacket is designed for most weather / temperatures as it is highly breathable. The tricot mesh inside the cycling jacket holds warm air and features thin fleece on the lower arms, lower back and neck. Vents on the back of jacket help excess warm air escape.
Being a cyclist you know that even when it is quite warm the airflow across your body can make things chilly, so all the features help to keep you at a comfortable temperature.
We treat every jacket with Nikwax to improve breathability and make them waterproof. We do this as we don't like to use nasty fluorocarbon coverings as they are bad for the environment. It also means that you can retreat the jacket yourself to keep its performance optimised.
We've tested the jacket under all conditions, we wouldn't recommend wearing it in extremely hot conditions, but why would you be wearing a jacket anyway? When it is really really hot!