Increasing temperatures tend to increase evaporation which leads to more precipitation. Increasing temperatures tend to increase evaporation which can lead to more precipitation. Lower elevations receive rain as most of their summer precipitation. Acid deposition also occurs via dry deposition in the absence of precipitation. Thunderstorms contribute over half of the annual precipitation. Average annual precipitation (rain and snow) is just under . The maximum average precipitation occurs in May. Winters are relatively cold with a precipitation decrease pattern. Mosquitoes are also highly sensitive to changes in precipitation and humidity. Lakes may form in basins where there is sufficient precipitation or meltwater from glaciers above. Its location makes the city vulnerable to flooding during seasons with above average precipitation. The maximum average precipitation occurs in December. Meteorologists use radar to monitor precipitation and wind. Its average annual precipitation is 790 millimetres. The mean annual precipitation is about , see climate table.