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: 25/08/2026 13:00
Week 1 – Monday 31st August to Sunday 06th September
Indications are that low pressure will dominate for the first week of September, leading to unsettled weather.
Temperatures are likely to be about average for the time of year, though may be above average towards the south.
Rainfall figures are showing wetter than average for the country as a whole.
Week 2 – Monday 07th September to Sunday 13th September
Although confidence in week 2 is lower, low pressure to the north of the country is likely to continue to dominate,
with temperatures remaining close to average for the time of year. Indications are for above average rainfall,
especially in northwestern areas.
Week 3 – Monday 14th September to Sunday 20th September
Uncertainty is increasing for week 3. There are indications that high pressure may move in, leading to more settled
conditions. Mean air temperatures are likely to be average to above average for the time of year, especially in the
south. Rainfall will be near average for most, with a signal for drier conditions for parts of the west and southwest.
Week 4 – Monday 21st September to Sunday 27th September
The confidence is low for week 4, although indications are that high pressure will continue to dominate, with above
average temperatures for the last week in September. Rainfall figures indicate that conditions will be drier than
normal across the country.
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.