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: 28/08/2026 13:00
Week 1 – Monday 31st August to Sunday 06th September
In week 1, a signal for lower pressure extends across the country. Higher than average rainfall is widespread with a stronger signal along the west and north Atlantic coast. Temperatures are also expected to be warmer than average for the time of year, with the exception of the far northwest.
Week 2 – Monday 07th September to Sunday 13th September
In week 2, confidence in the forecast decreases slightly but the signal for lower pressure remains. While the higher temperature signal becomes confined to the south and east, the trend for higher than average rainfall amounts remains.
Week 3 – Monday 14th September to Sunday 20th September
Uncertainty increases going into week 3. No clear signal for the steering pressure is evident how a slight signal for wetter than average conditions indicates that unsettled conditions will likely persist. Temperatures will generally be average across the country with a slightly peaked signal across Atlantic fringes.
Week 4 – Monday 21st September to Sunday 27th September
In week 4 there is little confidence in the forecast. No signal is evident for a steering pressure but given the fact that the higher than average signal remains for precipitation it is likely that conditions will continue unsettled with rain or showers. Temperatures are also signalled to be warmer than average across the southern half of 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.