So far in 2007, rainfall measurements in Berks County show normal amounts. Pennsylvania State Climatologist Paul Knight said about 36 inches has fallen since January. By contrast, only 50 percent of normal rainfall has occurred directly to the north of Berks, in Schuylkill County. "This is surprising since the sources of most of Berks County's rivers are located in Schuylkill County," Knight said. The Boyertown area's verdant fields this year, when all but seven of Pennsylvania's counties have issued a drought watch or warning, has been attributed to microclimates. Knight defines a microclimate as the long-term average on a fine scale. Factors contributing to microclimates include elevation, proximity to water bodies and land use. Microclimates show how terrain normally influences rainfall and impacts weather system movement. The effects are amplified in dry weather.Eastern and western sides of a county can switch from wet to dry and dry to wet over 60 days. "It could be a vicious little thunderstorm that ran up a ridge. Sometimes it is just a weird intersection of weather," Knight said. He expects the dry weather to continue to the end of November, but the cooling period is causing the atmosphere to shift gears.
Still, periods of dryness can be interrupted by robust periods of rain, which can lead to flooding.