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: 01/09/2026 11:00
Week 1 – Monday 07th September to Sunday 13th September
During week 1, low pressure will dominate Ireland’s weather with a predominantly westerly airflow over the
country. This will steer Atlantic frontal systems across Ireland through the period, with frequent showers and
spells of rain. Precipitation amounts will be above average as a result. Rainfall warnings cannot be ruled out. Air
temperatures will generally be around normal, but will be slightly higher than normal in parts of the south and east.
Week 2 – Monday 14th September to Sunday 20th September
There is potential for more settled weather during week 2 with a signal that high pressure will have more of an
influence over Ireland. This would bring more in the way of dry weather with rainfall amounts slightly below
average across the country. Temperatures are signalled to increase to slightly above average nationwide.
Week 3 – Monday 21st September to Sunday 27th September
While there is increasing uncertainty in week 3, current indications suggest that high pressure will remain close to
Ireland with the generally settled spell continuing. There will be a good deal of dry weather, though occasional
showers and spells of rain are possible. Rainfall amounts will remain below average across the country.
Temperatures will also remain slightly above normal for all areas.
Week 4 – Monday 28th September to Sunday 04th October
Confidence is low in the forecast for week 4. While there is a slight signal for nearby high pressure, there is no
clear trend for either settled or unsettled conditions during the period. There is the chance of drier than normal
weather in the south and west, with slightly wetter than average weather possible in the far northeast.
Temperatures will 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.