Updated 20th May - Covering the period 25th May - 16th June.
Mean temperatures will generally be 1.0 to 1.5C above the 1981-2010 long-term average but will be less than 1.0C above in Northern Ireland and in the west of Scotland. Warm weather early and late in the forecast period will outweigh fairly cool weather in Week 3.
Rainfall totals will continue to be mostly below normal, despite wet weather in Week 3, due to mostly dry weather early and late in the forecast period.
Sunshine totals are expected to also continue mostly above normal, though with a shortage of sunshine likely for north-west Scotland.
High pressure will cover the southern half of Britain for much of this week, bringing mostly warm dry sunny weather to most of England and Wales, though there will be occasional interruptions via weak fronts moving from west to east. It will often be cloudier over north Wales, north-west England, Northern Ireland and the north and west of Scotland, due to a prevailing west to south- westerly flow on the northern flank of the high pressure.
Rain belts will be more active in north-west Scotland, giving some persistent rain at times, but as the rain belts head further south and east they will tend to turn more showery, perhaps sparking off isolated thunderstorms towards the south-east on occasion. There is potential for a short-lived hot thundery plume to develop from the south towards the end of the week, but confidence in this is relatively low.
Mean temperatures are therefore expected to be above normal for the time of year, but not exceptionally so, with a positive anomaly in excess of 2C in parts of the east and south-east of England, but less than 1C in Northern Ireland and the west of Scotland.
Rainfall totals will tend to be below normal except in north-west Scotland, although there is slight potential for them to be swollen by thundery downpours in places near the end of the week.
Sunshine totals will most likely be below normal in Northern Ireland and western Scotland, and near normal in north-west England and north Wales. Elsewhere they will be above normal, particularly in the south and east of England.
This week is forecast to start off with changeable westerlies and low pressure coming closer to the north of Britain, and temperatures falling much closer to the seasonal norm. This will result in belts of rain crossing the country at frequent intervals. This unsettled regime is expected to fade late in the week with the winds slackening, resulting in a more showery type, followed by high pressure building from the south-west. Winds will probably become mostly north-westerly late in the week, so it will be near average to fairly cool for the time of year in most regions.
Mean temperatures are thus expected to be close to or just below the long-term normal in most parts of the country during this week, with negative anomalies of between 0 and 1C, but it will be a little warmer than average in eastern England, especially near North Sea coasts. Rainfall totals are expected to be above normal in most regions, especially in the west, where the week will start off somewhat wetter than average. Sunshine totals are expected to be close to or just below normal in most parts of the country.
Confidence is relatively low for this period but there are signs that a significant part of June will have relatively high pressure over Scandinavia, so the most likely outcome for this period is that we will see high pressure ridging from the Azores to Scandinavia, giving northern Britain further dry sunny weather, but bringing frequent easterly and north-easterly winds to the southern half of Britain in particular. This means that there will be plenty of dry and sunny weather for central and northern parts of the UK, but with the far north-west being more prone to seeing rain belts coming off the North Atlantic at times, and with the south being the most prone to rain belts and/or thundery outbreaks heading in off the near-Continent. There is also potential for eastern areas to see low cloud coming in off the North Sea, but the extent of any low cloud depends on how humid the air masses are, which is impossible to predict at this range.
As a result, most of the UK will be warmer, drier and sunnier than average during this period, but sunshine and temperatures are expected to be closer to normal in the north-west and south-east of the country, with temperatures also near normal close to the east coast of England generally. Rainfall totals are most likely to be below normal, though with more uncertainty over this for the
Monthly weather forecast
The month ahead forecast, written by Ian Simpson is updated once a week - every Monday. As with any longer term forecast, it's not possible to go into much detail and accuracy can tend to drop off toward the end of the period but it can still act as a very good guide to the weather during the upcoming month.