The temperatures in Porthmadog in September are quite cold with temperatures between 9°C and 15°C, warm clothes are a must.
You can expect rain for roughly half of the month of September in Porthmadog. We’re expecting roughly 8 to 15 days of rain, so your rubber boots and umbrella are going to see plenty of use this month if you’re keen on staying dry.
Our weather forecast can give you a great sense of what weather to expect in Porthmadog in September 2025.
If you’re planning to visit Porthmadog in the near future, we highly recommend that you review the 14 day weather forecast for Porthmadog before you arrive.
Temperatures
15° / 9°
Rainy Days
9
Snowy Days
0
Dry Days
21
Rainfall
138
mm
Sun Hours
6.0
Hrs
