BBC monthly outlook
Summary
Turning very warm for a time, but Lows threaten
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Wednesday 17 June – Sunday 21 June
Further showers and thunderstorms
The warm, humid and showery conditions will persist through the second half of the working week. On Wednesday and Thursday, thunderstorms are expected to develop once again, with southern England, central England, Wales, northwest England and southwest Scotland most likely to see the heaviest and most frequent of the showers. Frequent lightning, hail and heavy downpours are all possible in the these areas, bringing a risk of flash flooding in local spots.
Friday will be another day of showers, but this time the greatest risk of heavy showers and thunderstorms will be across Scotland. Later on Friday, showers should clear to give a spell of drier, calmer weather for a time, through Friday night and Saturday morning. However, with low pressure out to the northwest of the UK, it looks likely that a front will reach into Northern Ireland on Saturday afternoon, introducing outbreaks of rain and brisk winds. This front will track eastwards through the rest of Saturday and overnight into Sunday morning, bringing outbreaks of rain and breezy conditions for much of the UK.
The rain from this front will likely be heaviest in the north and west of the country, whilst southeast England may just see a spell of light rain. The front should clear on Sunday morning, but it will remain breezy through the rest of the day. Some showers are expected in the north and west of the country, whilst elsewhere it will be dry with some sunshine, particularly later on Sunday.
Monday 22 June – Sunday 28 June
Wet and breezy in the north and west at times
Through early next week, high pressure is expected to reach in from the southwest of the UK. This will bring plenty of dry and warm weather to England and Wales, with sunny periods for many. However, areas of low pressure will continue to persist out to the northwest of the UK, and these will likely give some showers or longer spells of rain to Scotland and Northern Ireland at times, although predominately to northwest Scotland.
Into the middle of next week, high pressure will build across the south of the UK and allow warmth to build in from continental Europe, becoming very warm for Wednesday and Thursday, with a chance of temperatures reaching into the high 20s Celsius in southeast England. There is some uncertainty on how long this hot spell will last across the southeast of the UK, but it seems likely that high pressure will weaken by the weekend, perhaps with showers developing.
As we lose the high pressure, we open the door to areas of low pressure encroaching from the northwest, which could introduce some wetter, breezier and cooler weather. This is most likely in the north and west of the country, whilst the south and east may well keep hold of the dry and warm conditions for a little longer through the weekend.
Monday 29 June – Sunday 12 July
Showers in the north, dry and warm in the south
For the end of June and the start of July, there may well be a battle ground over UK between high pressure and low pressure. Areas of low pressure are expected to be over Iceland and northern Europe, and these are likely to extend into the UK at times. Meanwhile, high pressure is expected to the southwest of the UK, extending into western Europe.
With low pressure to the north and high pressure to the south and southwest, there may be a north-south split in the weather for the UK. Northern areas can expect periods of wet, breezy and cool weather, whilst southern areas should be drier, calmer and warmer. This potential north-south split to the weather is likely to be the general theme through the first half of July. Frequent showers are possible in north and west Scotland, making it wetter than average here. Meanwhile, southeast England may turn out mostly dry, with just a few spells of rain.
After an exceptionally dry spring for the southeast, long periods of dry weather here will be unwelcome news for gardeners and growers. As we head towards the middle of July, it looks possible that there will be change in the weather pattern overhead. High pressure is expected to build over Europe and into the UK, which would result in increasingly dry, calm and warm conditions to much of the country.
Further ahead
We will take the forecast deeper into July. Could we see dry, calm and warm conditions developing in mid-July and persisting through the rest of the month?
https://www.bbc.co.uk/weather/outlook