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
MONTHLY FORECAST, ISSUED TUESDAY 16 SEPTEMBER 2025
Week 1 (Monday 22 September to Sunday 28 September)
Week 1 is indicating rather unsettled conditions. The overall signal is for low pressure to to the southwest of Ireland to be the dominant force resulting in wetter than average conditions across much of the country. Mean air temperatures will likely be close to or slightly below normal for the time of year.
Week 2 (Monday 29 September to Sunday 05 October)
While confidence in week 2 is lower, there is little change indicated in week 2. Low pressure looks to continue to dominate conditions with the precipitation anomaly indicating wetter than average conditions this week. Mean air temperatures are likely to be around normal for the time of year.
Week 3 (Monday 06 October to Sunday 12 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. Overall there is a signal more settled conditions this week as the precipitation anomaly indicates for drier than average conditions while mean air temperatures will remain around average this week.
Week 4 (Monday 13 October to Sunday 19 October)
In week 4 the forecast confidence is low. There is a slight signal for low pressure to the north of Ireland potentially bringing more mixed conditions this week. There is a signal for rainfall amounts along the west and north coasts to be wetter than average while the east coast signals drier than average conditions for week 4. Again, mean air temperatures will likely continue around average for the time of year.
Seasonal Outlook for September October November (SON)
The signal from the C3S seasonal models for Ireland during the September October November (SON) period is for above average temperatures, with average rainfall overall.
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 over the three-month period.
The rainfall forecast is less certain, with the potential for both wetter and drier periods through the Autumn season. There is however a higher signal for drier periods in October at times.
The sea surface temperatures around Irish coasts are expected to be above average during SON, trending 0.5 to 2.0°C higher than normal.