district. Manhattan has two central business districts, the Financial District at the southern tip of the island, and Midtown Manhattan. The term uptown also refers to the northern part of Manhattan above 72nd Street and downtown to the southern portion below 14th Street, with Midtown covering the area in between, though definitions can be rather fluid depending on the situation. Fifth Avenue roughly bisects Manhattan Island and acts as the demarcation line for east/west designations (e.g., East 27th Street, West 42nd Street); street addresses start at Fifth Avenue and increase heading away from Fifth Avenue, at a rate of 100 per block on most streets. South of Waverly Place, Fifth Avenue terminates and Broadway becomes the east/west demarcation line. Although the grid does start with 1st Street, just north of Houston Street (the southernmost street divided in west and east portions; pronounced HOW-stin), the grid does not fully take hold until north of 14th Street, where nearly all east–west streets are numerically identified, which increase from south to north to 220th Street, the highest numbered street on the island. Streets in Midtown are usually one-way, with the few exceptions generally being the busiest cross-town thoroughfares (14th, 23rd, 34th, and 42nd Streets, for example), which are bidirectional across the width of Manhattan Island. The rule of thumb is that odd-numbered streets run west, while even-numbered streets run east. Climate Under the Köppen climate classification, using the isotherm, New York City features both a humid subtropical climate (Cfa) and a humid continental climate (Dfa); it is the northernmost major city on the North American continent with a humid subtropical climate. The city averages 234 days with at least some sunshine annually. The city lies in the USDA 7b plant hardiness zone. Winters are cold and damp, and prevailing wind patterns that blow offshore temper the moderating effects of the Atlantic Ocean; yet the Atlantic and the partial shielding from colder air by the Appalachians keep the city warmer in the winter than inland North American cities at similar or lesser latitudes such as Pittsburgh, Cincinnati, and Indianapolis. The daily mean temperature in January, the area's coldest month, is ; temperatures usually drop to several times per winter, and reach several days in the coldest winter month. Spring and autumn are unpredictable and can range from chilly to warm, although they are usually mild with low humidity. Summers are typically warm to hot