A number of First Glasgow B9TL's were fitted with air conditioning upstairs but standard opening windows have now been fitted. Air conditioning is also fitted to majority of London Buses, one example being the NBFL Routemaster which had opening windows retrofitted.

In 2026, the presence of air conditioning on UK buses remains a "mixed bag" depending on the region and the age of the fleet. While most modern electric and hydrogen buses introduced in cities like London, Manchester, and Birmingham are equipped with climate control systems, many older diesel buses still rely on "forced air ventilation" and opening windows. In London, nearly all newer "New Routemaster" and zero-emission buses have systems designed to keep the interior comfortable, though they are often criticized for not being as powerful as AC units found in hotter climates. On long-distance coaches like National Express or Megabus, full air conditioning is a standard feature and is almost always functional. For local provincial buses in the North or South West, you are much less likely to find AC, as the UK's historically temperate climate meant it wasn't a priority for bus operators until the more frequent summer heatwaves of the 2020s. If you are traveling on a particularly hot day, the upper deck of a double-decker bus can still get quite warm despite modern ventilation.