Northern lights in Milwaukee: tonight’s chance

A lakefront city that faces east

Milwaukee's identity is its lakefront, but for the aurora the lake sits on the wrong side. The shore runs roughly north to south, so the open water lies east of downtown and the northern horizon follows a line of suburbs up the coast. On a storm night the darkest direction from the lakefront is northeast, over the water, and that is often where the first glow shows. The bluffs north of downtown, along the residential lakeshore, lift you above the beach and give that northeast view, but the true north there is still lit.

The better answer is often inland. Northwest of the city, the Kettle Moraine country is a landscape of glacial hills, kettle lakes and forest, much darker than the shore. Pick a hilltop or an open field rather than a hollow, because the moraine's knobs can hide a low aurora as easily as a building can.

A moderate storm, with little room to spare

At 52.4 degrees magnetic latitude, Milwaukee is about where the NOAA scale's second level begins to reach. The threshold, Kp 6.5, means the aurora rises into view in the north during G2 (Moderate) storms, and the Kp index page explains how to read the three-hour blocks of the forecast. Overhead aurora needs about Kp 6.8, so the nights when the whole sky lights up belong to the strong storms of the solar cycle. Madison, inland, sits at almost the same magnetic latitude; what separates the two cities is the lake's effect on cloud, not the storm needed.

The lake's cloud calendar

Milwaukee's cloud year is different from that of inland Wisconsin. Lake Michigan warms slowly, so it stays cold into late spring, and humid air crossing it then tends to condense into low stratus and fog along the shore. In NASA POWER averages, that pushes May to 80%, the cloudiest month of the year. Late summer reverses the pattern: the lake is warm, the air is drier, and September reaches the lowest cloud amount at 60%. On December 15, full darkness runs from 6:00 PM to 5:34 AM, plenty of time if a storm and a clear spell coincide. The Wisconsin page compares the rest of the state, and the Chicago page covers the other big city on the same shore.