done in Raleigh, North Carolina conducted on Parthenolecanium quercifex (oak scales), showed that this particular species preferred warmer climates and were therefore found in higher abundance in urban habitats than on oak trees in rural habitats. Over time spent living in urban habitats, they have adapted to thrive in warmer climates than in cooler ones. The presence of non-native species is heavily dependent on the amount of human activity. An example of this can be found in the populations of cliff swallows seen nesting under the eaves of buildings in urban habitats. They make their homes using the shelter provided by humans in the upper regions of homes, allowing for an influx in their populations due to added protection and reduced predator numbers. Other impacts on weather and climate Aside from the effect on temperature, UHIs can produce secondary effects on local meteorology, including the altering of local wind patterns, the development of clouds and fog, the humidity, and the rates of precipitation. The extra heat provided by the UHI leads to greater upward motion, which can induce additional shower and thunderstorm activity. In addition, the UHI creates during the day a local low pressure area where relatively moist air from its rural surroundings converges, possibly leading to more favorable conditions for cloud formation. Rainfall rates downwind of cities are increased between 48% and 116%. Partly as a result of this warming, monthly rainfall is about 28% greater between to downwind of cities, compared with upwind. Some cities show a total precipitation increase of 51%. Research has been done in a few areas suggesting that metropolitan areas are less susceptible to weak tornadoes due to the turbulent mixing caused by the warmth of the urban heat island. Using satellite images, researchers discovered that city climates have a noticeable influence on plant growing seasons up to away from a city's edges. Growing seasons in 70 cities in eastern North America were about 15 days longer in urban areas compared to rural areas outside of a city's influence. Research in China indicates that urban heat island effect contributes to climate warming by about 30%. On the other hand, one 1999 comparison between urban and rural areas proposed that urban heat island effects have little influence on global mean temperature trends. One study concluded that cities change the climate in area 2–4 times larger than their own area. Other suggested that urban heat