This all depends on where you live and is based on the “normal” climate there.
Met Office heatwave criteria sets the temperature for a heatwave at 25C in Scotland, Northern Ireland, much of Wales and northern England.
For many other areas of England, as well as south-east Wales, it is 26 or 27C. In London, most of the home counties and Cambridgeshire, it is 28C.
These thresholds must be reached or exceeded on at least three consecutive days.
It is possible that many areas will officially be classed as being in a heatwave when Sunday’s temperatures are confirmed.
For some areas it is likely to turn into a prolonged heatwave.