The extended range forecast, which includes the monthly and seasonal forecasts, can at times provide an insight into weather patterns in the months ahead. However, they should not be used for specific planning purposes as they have generally low skill compared with the 10-day forecast. This is because forecasts beyond one week become increasingly uncertain due to the chaotic nature of the atmosphere. Further information can be found here: Monthly and seasonal forecast explained.
Images: Shutterstock/gabriel12. Met Éireann HQ during Storm Emma 2018
Issued: 18/08/2026 12:00
Week 1 – Monday 24th August to Sunday 30th August
There is a signal for low pressure to dominate with rainfall amounts generally a bit above average for the time of
year, particularly in the south. Temperatures are generally forecast to be average for the time of year or a little
higher in the south and east.
Week 2 – Monday 31st August to Sunday 06th September
A similar story for week two with low pressure expected to be dominant. Rainfall amounts will again be a bit above
average for most, particularly near western Atlantic coasts. Temperatures will be average for the time of year,
possibly a little bit above in the south.
Week 3 – Monday 07th September to Sunday 13th September
There is a weak signal that high pressure over the continent will extend a ridge of high pressure close to or over
Ireland. Temperatures are forecast to be slightly above average across the country, as will rainfall amounts.
Week 4 – Monday 14th September to Sunday 20th September
While confidence is low this far out, there is a signal for high pressure to become dominant, bringing with it slightly
above average temperatures and slightly below average rainfall amounts.
Seasonal Outlook for September, October and November (SON)
The signal from the C3S seasonal models for Ireland during the SON period is for above average temperatures. Rainfall amounts will be close to or lower than normal in September but we will see a transition to wetter, more unsettled conditions in October and November.
Mean temperatures during SON are signalled to be above average overall. Temperatures are likely to trend between 0.5 and 1.0°C above average through the three months.
The rainfall forecast across SON varies. There is potential for normal or slightly drier than normal conditions during September. However, there is a signal for wetter than average conditions in October and November.
The sea surface temperatures around Irish coasts are expected to be above average during SON, trending 0.5 to 2.0°C degrees higher than normal generally. Sea surface temperatures are expected to be highest in comparison to average during September.