“Al fresco” means literally “in the fresh”, as in “in the fresh air, outside.”
It usually refers to dining outside. It can also be used to mean a picnic in the country, eating at outdoor tables at a café, or in your own back-yard or garden.
Al fresco dining, which has long been common in Europe, only started to catch on in the UK and North America towards the end of the 1900s.
Now, in the UK and North America, the “al fresco” season starts very early, with people bundled up in ski jackets or rain coats sitting outside in weather that an Italian or French person would think was nuts. Many establishments now cover their patios, and heat them with space heaters.
In some places, such as Florida, which gets too hot during the summer to eat outside, people flock indoors to eat in air-conditioned comfort.
The one place perhaps where you can dine al fresco without worrying about flying insects is on cruise ships. They only appear when you are anchored.
“Al fresco” only means “out doors”. It does not mean, as something people think, “out doors without clothes”. That is “al freddo”.