From Meto
"Here is an update for the weather today and over the weekend.
We are now under the influence of a very warm, moist plume of air which is likely to give us the hottest day of the year so far. It will be mainly fine and dry this afternoon with temperatures rising to high 20s or low 30s. A Heat wave Level 2 has been issued for Friday and Saturday.
Tonight and tomorrow remains our main concern. As we move into this evening we will see heavy, thundery showers developing. These showers will move north during the night, generally clearing in the morning. The showers could be torrential at times and accompanied by frequent lightning, large hail and strong gusty winds leading to significant impacts in places. We could see 10-20 mm of rain quite widely overnight with some places seeing 30-40 mm. It is possible that in particularly heavy showers some places could see 50-75 mm in 3 hours, 30 mm or more in an hour.
When this first area of showers has cleared there will be a dry period with good sunny spells during the morning but as the temperatures rise further heavy showers and thunderstorms will develop during the afternoon. These showers are expected to clear during the evening to leave a rather cloudy but dry night.
Confidence: There is still some uncertainty about the exact location of the heaviest showers. Most of the country will see heavy showers and thunderstorms at times. The forecast currently suggests that the areas at greater risk from more extensive heavy showers and thunderstorms overnight are the Thames Valley, Surrey, West Sussex and Hampshire & Isle of Wight. This does not mean that areas further east will not see some showers but they do not seem to be as widespread. This will need to be watched carefully and I would recommend keeping an eye on Hazard Manager to see where the heaviest showers are developing.
Warnings: The Met Office will be upgrading the warning soon to an Amber RAIN Warning (Medium Likelihood of Medium Impacts) covering the areas at highest risk from the heavy showers, namely the Thames Valley, Surrey, West Sussex, Hampshire & Isle of Wight. They will also updating the Yellow RAIN Warning (Low Likelihood of Medium Impacts) to cover the rest of the area, namely East Sussex and Kent. Impacts could include surface water flooding, flooding on fast responding urban catchments, power outages due to lightning strikes as well as poor driving conditions, transport issues and problems for outside events.
Sunday will still be very warm and quite humid with isolated heavy showers or thunderstorms developing during the day, gradually clearing during the evening. Monday and Tuesday look like being mainly fine and dry with variable amounts of cloud although isolated showers are still possible. Remaining warm or very warm."
North downs, near Folkestone, 177m asl.