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: 08/09/2026 13:00
Week 1 – Monday 14th September to Sunday 20th September
Changeable conditions are forecast to continue next week, with low pressure systems tracking to the north of Ireland and high pressure to the south. This will lead to spells of rain or showers and breezy conditions at times, interspersed with drier and calmer periods. With the low pressure systems passing to the north, the highest rainfall accumulations are expected in the north and west, while rainfall amounts remain below average in the south and east. Temperatures are expected to be above normal for mid-September.
Week 2 – Monday 21st September to Sunday 27th September
High pressure is forecast to become more of a dominant feature during this period, bringing below average rainfall and near or above average temperatures.
Week 3 – Monday 28th September to Sunday 04th October
There is a signal for a change to slightly more unsettled weather during this period. Pressure is expected to be higher than average overall, so there is likely to be some dry weather, however rainfall amounts are expected to be above normal in the north and west, so low pressure is likely to be an influence at times, bringing some rain or showers. Temperatures are expected to be near or slightly higher than normal.
Week 4 – Monday 05th October to Sunday 11th October
The signal for week beginning the 5th of October is weak, so there is high uncertainty in the forecast for this period. It is possible that the weather will be mixed, leading to below average rainfall in some areas and above average rainfall in other areas. Temperatures are forecast to be close to normal.
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.