In September, Portsmouth typically sees daytime highs of 17.9°C and overnight lows around 10.5°C. Compared to the annual average high of 13.2°C, September runs +4.6°C.
September in Portsmouth averages a daytime high of 17.9°C and an overnight low of 10.5°C.
September runs +4.6°C compared to Portsmouth's annual average high of 13.2°C, ranking #4 of 12 months by warmth.
Plan for daytime highs near 17.9°C and cooler evenings around 10.5°C.