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: 11/09/2026 14:00
Week 1 – Monday 14th September to Sunday 20th September
Week 1 is indicating Ireland lies between high pressure to the southwest in the Atlantic and low pressure to the
northeast. 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
While confidence in week 2 is lower, there is a slight signal for higher pressure to dominate conditions this week.
More settled conditions are expected this week with signals for below average rainfall and near or above average
temperatures.
Week 3 – Monday 28th September to Sunday 04th October
There is increasing uncertainty in the forecast for week 3. There is no signal for either high or low pressure to
dominate our weather this week. Rainfall amounts and mean air temperatures will be around average for the time
of year.
Week 4 – Monday 05th October to Sunday 11th October
In week 4 the forecast confidence is low. Again, no strong signal for either higher or lower pressure to dominate.
The precipitation signal for this week is slightly leaning towards wetter than average conditions, while
temperatures look to be close to or above average.
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.