Warmth far more fitting of July than the last of September will spread over the UK this week.

Temperatures will soar as many as 10 degrees C above normal, with Wednesday through Friday being warmest for the UK as a whole. Historical record highs could be reached.

For example, in London, the warmest daytime will reach about 27 degrees C (near 80 F). Normal highs this time of year are 16-17 degrees C (61-63 F). It will be about this warm elsewhere in South and East England, together with the Midlands.

Warmest daytimes in Scotland and Northern Ireland will see readings to at least 21-23 degrees C (70-74 F).

The trigger for the exceptional warmth will be strong high pressure building northward towards southern Scandinavia from the Alps. This high will shunt the Atlantic jet stream and the normal cool maritime flow well northward, west of the British Archipelago.

A cold front will break the exceptional warmth near the end of the week, but not any truly cold weather.