Click on a day for an hourly weather forecast
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.
| Month | Temperatures | Rainy Days | Dry Days | Snowy Days | Rainfall | Weather | More details |
|---|---|---|---|---|---|---|---|
| January | 5° / 2° | 13 | 10 | 9 | 194 mm | Awful | Porthmadog in January |
| February | 6° / 2° | 12 | 9 | 8 | 179 mm | Awful | Porthmadog in February |
| March | 8° / 2° | 11 | 15 | 5 | 142 mm | Awful | Porthmadog in March |
| April | 11° / 4° | 8 | 20 | 2 | 104 mm | Awful | Porthmadog in April |
| May | 13° / 6° | 10 | 21 | 0 | 136 mm | Bad | Porthmadog in May |
| June | 16° / 9° | 10 | 20 | 0 | 155 mm | Ok | Porthmadog in June |
| July | 17° / 11° | 9 | 22 | 0 | 150 mm | Ok | Porthmadog in July |
| August | 17° / 11° | 10 | 21 | 0 | 158 mm | Ok | Porthmadog in August |
| September | 15° / 9° | 9 | 21 | 0 | 138 mm | Ok | Porthmadog in September |
| October | 12° / 7° | 11 | 20 | 0 | 191 mm | Bad | Porthmadog in October |
| November | 8° / 5° | 13 | 15 | 2 | 203 mm | Awful | Porthmadog in November |
| December | 6° / 3° | 14 | 11 | 6 | 223 mm | Awful | Porthmadog in December |