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: 04/09/2026 13:00
Week 1 – Monday 07th September to Sunday 13th September
Ireland will be under the influence of low and high pressure. While a ridge of high pressure will move
during the midweek section, bringing mostly dry and calm weather, low pressure is signalled to dominate on either
side. Overall though, rainfall projections are expected to be around normal with an Atlantic flow steering in frontal
band of rain or showers, and oftentimes breezy conditions.
Week 2 – Monday 14th September to Sunday 20th September
There is a reasonably consistent signal that high pressure will move in across the country, bringing a
settled phase of weather, at least early on the period. As a result, mostly dry and calm weather can be expected.
Much drier than usual conditions are also anticipated with some milder or warmer than average temperatures
also.
Week 3 – Monday 21st September to Sunday 27th September
While there is increasing uncertainty during week 3, current indications suggest that high pressure will remain
close to Ireland bringing mixed conditions. While there should be a good deal of dry weather, occasional showers
and spells of rain are possible too. Rainfall amounts may remain below average across the country. Indications
are for close to or slightly above normal temperatures also.
Week 4 – Monday 28th September to Sunday 04th October
Confidence is low in the forecast for week 4. There is no clear trend for either settled or unsettled conditions.
Nonetheless, mean temperatures may trend slightly above normal but with slightly wetter than usual conditions
too.
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.