Portsmouth and Southampton climate by month
Warmest month: July (highs about 23°C). Coolest: January (about 9°C). Wettest: November (100 mm). Driest: July (44 mm).
Source: Met Office, Southampton, Mayflower Park, 1991-2020 averages (Open Government Licence v3.0). Daylight is calculated from the latitude of Portsmouth and Southampton for the 15th of each month. Southampton, Mayflower Park is on the waterfront next to Southampton's old town, so these figures describe Southampton itself. Portsmouth is about 25 km east; the nearby Solent station (gcp0yzhp4) publishes no sunshine or rain-day figures, so it was not used.