1. By their behavior exactly, you can predict the weather for the next day. So, there is an opinion that if the mosquitoes swarm (i.e. fly together), it's good weather – calm, Sunny, hot. Conversely, there is an opposite belief that it is the rain.
2. Weather can be predicted at any point of our country. Mosquitoes on earth for many thousands of species. Each has its own distinct characteristics. For example, the mosquito-Chironomidae, who lives on the coasts of Azov and the Caspian sea, thrives in wet weather. When it comes to the drought, the Chironomidae "lies" under damp leaves, in the lowlands. That is, this kind of swarming in anticipation of cloudy weather.
3. Mosquitoes breed only in dry weather. But other species of mosquitoes that are common in the Central region of Russia, for example the mosquito telkonet, hot weather like they are in heat form a swarm to breed. When the weather is dry, they can all fly. And when raining or cold and you can't, because they have raw wings. It happens in flight, the breeding of mosquitoes.