Monthly Outlook

Unsettled weather is expected to dominate through late August and early September, with occasionally heavy rain and thunderstorms.

By mid-September, high pressure may build and bring a return to drier conditions, most probably the south.

Occasional downpours and thunderstorms

On Wednesday, a low pressure circulation to the southwest will start to push frontal systems towards the UK. A plume of warm, humid and increasingly unstable air will spread northwards, causing scattered sharp showers to develop across England, Wales and Northern Ireland, while Scotland should stay largely dry for now, at least in the north. Later in the day, overnight and into Thursday, these may become more widespread and locally heavy, with a risk of strong thunderstorms developing.

Downpours may lead to localised flooding, and frequent lightning is possible. As Thursday wears on and low pressure progresses northeastwards, showers should reach Scotland while the southern UK becomes drier.

The rest of the week will remain unsettled, with further showers or more persistent rain but some sunshine in between. With winds turning mainly northwest to southwesterly, conditions will become less warm and humid, although temperatures should still fluctuate around the late-August average. Some heavy and thundery outbreaks of rain will remain possible, perhaps becoming more likely through Saturday and Sunday when winds could become rather strong and gusty in places.

Remaining unsettled

A disturbed weather pattern is likely to continue into the first week of September, with a series of low pressure systems and associated fronts likely to pass close to or across the UK. These should bring bouts of rain, heavy at times and potentially thundery, occasionally accompanied by strong and gusty winds. Rainfall may again be intense enough to bring a risk of local flooding.

In between weather systems there should be transitory high pressure ridges delivering temporary calmer and drier spells, with some sunshine and a few showers here and there. Temperatures are going to be variable from day to day but on average, despite the rain, they are more likely to be near or slightly above average for the week rather than below.

Later in the week there are some hints that high pressure may start to build more strongly to the south. This could mean that the southern UK might have a drier and warmer trend, although maybe only for a couple of days, while northern and some western regions perhaps stay wetter.

Turning drier and warmer, at least in the south

Atlantic weather systems may continue to dominate conditions into the first week of September, so further periods of wet and windy or showery weather look most likely, with short-lived drier and sunnier spells in between. The north and west may be wetter than the south and east. Temperatures are most likely to be near or slightly above normal.

By the second week of September there are signs of a possible change. High pressure could begin building again across continental Europe, and this may push warmer air towards the UK, with temperatures ending up further above the September average, highest across southern England. Conditions should become drier and less windy as well, but initially that's more likely across the southern UK than the north.

It may still be wetter in parts of the northern UK, especially across Scotland, but eventually high pressure may settle across the UK, delivering more settled weather to a greater area.

In Friday's update, the outlook will take us into late September. We will see if there are still signs of a more settled and warmer period after the disturbed pattern of the next couple of weeks.