Normandy enjoys a temperate oceanic climate, with minor seasonal differences in temperature and mild, but sometimes very snowy, winters, with temperatures of around 2–3°C and summers that are far from stifling, the temperature hovering at around 20°C. Autumn and winter see many a rainy day, the rainiest months being October, November and January.
There is a strong ocean influence on the climate of Lower Normandy. On the coast, differences in temperature are modest and rainfall is frequent. From the Caen plain to the Normandy hills, the amount of rainfall depends on altitude, some areas having twice as much rain as others. While the coastal regions enjoy milder winters and sunnier summers than inland areas, they are also subject to more sustained wind. Sometimes the climate reveals a more extreme side, producing heat waves, periods of snow, torrential rain and drought.
Upper Normandy also has an oceanic climate, resulting in mild temperatures and a fair amount of rain.
Winter temperatures generally remain above freezing: an average of 5°C in January on the coast, and 4°C further inland. Summers are cool: an average of 17°C in July, both inland and on the coast.
In practice, these figures hide significant disparities, particularly in terms of rainfall. While the Bolbec area (Seine-Maritime) records average annual rainfall of 1100mm, the south-eastern area of the Eure department has only half as much, with less than 550mm of rain per year, which is similar to the amount that falls on Marseille and Nice (of course, the type of rainfall and how it is distributed across the year are not the same). This is because this particular part of the Eure department is protected by the hills of the Perch area, where the warm air masses release all their precipitation.