Due to the city's location in the Midwestern United States, Milwaukee experiences a continental climate with wide variations in temperatures over short periods, especially in spring and autumn. The warmest month of the year is July, when the average high temperature is 81 °F (27 °C), and the overnight low is 63 °F (17 °C). The coldest month of the year is January, when the average high temperature is only 28 °F (-2 °C). Low temperatures in January average 13 °F (-11 °C).

The highest temperature ever recorded in Milwaukee is 105 °F (41 °C) on July 17, 1995. The coldest temperature ever officially recorded at Milwaukee is -26 °F (-32 °C), on both January 17, 1982 and February 4, 1996. The former occasion is referred to as "Cold Sunday," due to the extreme cold felt in many locations in the United States on that day. .

Milwaukee's climate allows for a wide variation in both type and amount of precipitation throughout the year. Rain can fall all year round, but is rare during winter months such as December, January, and February. It only occurs in these months when combined with unseasonably warm weather, as the high temperatures in these months are frequently below the freezing point of water. Snow falls in and around Milwaukee regularly from late November until early March. However, snow can fall as early as late September, or as late as the end of May. During the transition into and out of winter, various mixed forms of precipitation can occur, such as sleet, ice, and freezing rain. Ice storms, while rare, are not impossible. These types of precipitation tend to occur mainly in November and March, due to these months serving as transitions between winter and more mild seasons.

An average year in Milwaukee sees 34.81 inches (884.2 mm) of precipitation, with a yearly average snowfall of 47.0 inches (119 cm) . The city receives more snowfall than cities even slightly inland, due to lake effect snow produced by Lake Michigan. Milwaukee lies on the western shore of Lake Michigan, east winds, although not the prevailing wind direction in the Midwest, do occur when Panhandle Hook systems move northeast bringing heavier snowfall on the Milwaukee side of the lake. Milwaukee receives far less snow than cities on the eastern shore of the lake, which receive extra snowfall when more common west or north-west winds blow. However, just like every other aspect of Milwaukee's weather, the amount of snowfall in any given winter season is highly variable; the month of December 2000 saw 49.5 inches (126 cm) of snow, more than the annual average. However, almost no snow fell in the remaining months of the 2000-2001 snow season, with January recording just under 2.0 inches (5 cm) . During the 2007-2008 winter season, Milwaukee recorded 99.1 inches (251.7 cm).

The wettest month of the year is August, when 4.03 inches (102 mm) of precipitation falls, mainly as rainfall due to thunderstorms. Long-duration rain events are uncommon in the summer months, usually occurring only in April or October. Thunderstorms are the main precipitation events from May until September, and Milwaukee experiences an extended tornado season which lasts from late March until early June, however, severe weather and tornadoes are more frequent inland to the west. The driest month is February, when only 1.65 inches (41.9 mm) of precipitation falls, almost entirely as light, low moisture content snow resulting from the Alberta Clipper type system when cold, dry air masses dominate.