Calais sees a significant rise in temperature during May. The monthly average is 55°F (12.8°C), a significant increase from April's 48.5°F (9.2°C) average, making May the official start of the summer season.
Low temperatures can still barely reach the high 40s at 49.8°F (9.9°C), but the highs climb just into the 60s at a pleasant 61.2°F, which would be 16.2°C.
To celebrate this time of year, Calais hosts an annual hiking competition, the Rond'Opale. All of this takes place along the Opale coast.
The competition is attended by outdoor enthusiasts, walkers, joggers and runners from around the world. Some of its appeal lies in the breathtaking views along the trails. Another attractive feature of the competition is the variety of trials, from beginner levels that can be leisurely strolled to extremely advanced courses for the most prime of athletes.
Some brave souls may find the sea warm enough for swimming when properly attired in wetsuits or other appropriate swimwear, but most will probably still find it too cold to venture into. However, all of Calais' aquatic activities such as fishing and sailing are still on offer.
The days are slightly longer during the summer. There is about 1.6" (41.6 mm) of precipitation falling on roughly 12 days per month.
