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: 25/09/2026 14:00
Week 1 – Monday 28th September to Sunday 04th October
In week 1, low pressure in the Atlantic is expected to dominate the weather bringing unsettled conditions. In
particular, a deep low pressure system in the Atlantic is expected to move close to Ireland on Tuesday, bringing a
spell of wet and windy weather. Temperatures are expected to be above average for the period. Rainfall amounts
are also expected to be above average, particularly in the south and west.
Week 2 – Monday 05th October to Sunday 11th October
While confidence in week 2 is lower, the signal for low pressure wanes, but is still expected to be the dominant
feature of the week’s weather. Temperatures are expected to remain slightly above average, with rainfall amounts
also slightly above average for the time of year.
Week 3 – Monday 12th October to Sunday 18th October
There is increasing uncertainty in the forecast for week 3, but signals are for a similar story to the previous week,
with low pressure continuing to dominate, and temperatures and rainfall remaining above average for the time of
year.
Week 4 – Monday 19th October to Sunday 25th October
In week 4, the confidence in the forecast is low. There is little signal for either high or low pressure to dominate.
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.