A marked warming trend this week, from the south of the UK from Wednesday onwards. It will become increasingly humid. The air will become unstable and this brings the risk of some thundery downpours by the end of the week.
There is a level of uncertainty at present as to how unstable the air over the UK may become - in terms of timing and how far north the risk will extend. Current thinking is that thundery downpours will gradually extend northeast on Friday with further downpours possible on Saturday. These are most likely during the afternoons, and the Met Office now have a weather warning in place for the risk of disruption (see below).
Daytime highs are expected to peak on Friday before dipping a little into the weekend, but still remaining warm. Northern England could get highs 21-28°C (to 82F) with temperatures further south possibly rising above 30°C - making it as warm or warmer than many holiday hotspots across the continent.
There is the potential for the development of large thunderstorms over England and Wales from early on Saturday. In this situation large amounts of energy are available in the atmosphere and this coupled with high moisture content can lead to torrential downpours along with frequent lightning activity, hail and locally strong gusts. In this situation many elements need to come together at the same time to form these thunderstorms and so there remains large uncertainty in their development.
This alert is therefore likely to be updated in the coming days