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: 18/09/2026 14:00
Week 1 – Monday 21st September to Sunday 27th September
A frontal wave to the west of Ireland on Monday is forecast to move in over the west and north of the country on
Tuesday before tracking eastwards across other areas during Tuesday night and Wednesday. High pressure is
then expected to build briefly, before low pressure systems track to the northwest of the country later in the week,
bringing further spells of rain or showers. Rainfall amounts are expected to be lower than average in the south and
southeast, but higher than average elsewhere. Temperatures will fluctuate due to the changeable conditions, but
are expected to be higher than normal overall. There is a chance of rain warnings during this period.
Week 2 – Monday 28th September to Sunday 04th October
There is a signal for unsettled weather for the end of September and start of October, with low pressure
dominating. Rainfall amounts are forecast to be higher than normal nationwide and there will likely be breezy or
windy conditions at times, so there is a chance of weather warnings. Temperatures are expected to be near or
slightly higher than normal.
Week 3 – Monday 05th October to Sunday 11th October
A typical pressure pattern is forecast for Week 3, with some unsettled spells of rain and showers contributing to
above normal precipitation. Temperatures are forecast to be slightly higher than normal.
Week 4 – Monday 12th October to Sunday 18th October
It is possible that high pressure will be more dominant for Week 4, bringing drier and cooler conditions. Both
rainfall and temperatures are forecast to be lower than average during this period.
Seasonal Outlook for October, November, December (OND):
The signal from the C3S seasonal models for Ireland during the OND period is for above average temperatures. Rainfall amounts are also likely to trend above average with a strong signal for wet and unsettled conditions at times during OND.
Mean temperatures during OND are signalled to be above average overall. Temperatures during the period are likely to trend between 0.5 and 1.0°C above normal. However, colder than average periods, where winter hazards are possible, could still occur at times towards the end of OND.
The rainfall forecast for OND signals the potential for above average rainfall throughout the period, especially in the south. The highest likelihood for wetter than average conditions are signalled during November.
The sea surface temperatures (SSTs) around Irish coasts are expected to continue above average during OND, trending 0.2 to 1.0 degrees higher than normal generally.