, Lehigh County's largest city, at Christmas 2017 , part of the
Appalachian Mountain range in Lehigh County, with
Allentown in the foreground in December 2010 , a
tributary of the
Delaware River, in Lehigh County near
Slatington in June 2007 Lehigh County has a total area of , of which is land and (0.9%) of which is water.
Topography Lehigh County borders two
Appalachian mountain ridges. To the north, the county borders
Blue Mountain, which has an altitude of . To the south, it is bordered by
South Mountain, which has an altitude of and cuts through the southern portions of both Lehigh and Northampton counties. The Lehigh County's highest point is near
Germansville at
Bake Oven Knob, a mass of
Tuscarora conglomeratic rocks that rise about above the main Blue Mountain ridge in northwestern
Heidelberg Township. Lehigh County is part of the
Delaware River watershed. Most of the county is drained by the
Lehigh River and its tributaries, though the
Schuylkill River also drains regions in the county's south through
Perkiomen Creek and in the county's northwest through
Maiden Creek.
Adjacent counties •
Carbon County (north) •
Northampton County (northeast) •
Bucks County (southeast) •
Montgomery County (south) •
Berks County (west) •
Schuylkill County (northwest)
Climate Lehigh County's climate falls in the
humid continental climate zone. The variety is hot-summer (
Dfa) except in the county's higher elevation areas, where it is warm-summer (
Dfb). Summers are typically hot and muggy, fall and spring are generally mild, and winter is cold. Precipitation is almost uniformly distributed throughout the year. In
Allentown, January lows average and highs average . The lowest officially recorded temperature was in 1912. July lows average and highs average with an average relative humidity of 82%. The highest temperature on record was in 1966. Early fall and mid-winter are generally driest with October being the driest month with only 74.7 mm of average precipitation. Snowfall is variable with some winters bringing light snow and others bringing numerous significant snowstorms. Average snowfall is per year, with the months of January and February receiving the most now with just over in each of these months. Rainfall is generally spread throughout the year with eight to twelve wet days per month, at an average annual rate of . The
hardiness zone in the majority of the county has increased from 6b to 7a. 6b still exists in some northern and higher areas. }} ==Demographics==