07/14/2026
The Water Around the Apostle Islands Just Dropped 24 Degrees Overnight. Here's Why.
If you're planning to get in the water near the Apostle Islands this week, read this first. A buoy near McQuade Harbor on the North Shore read close to 70°F yesterday afternoon. By this morning it was 46°F. That's a 24-degree plunge in less than a day.
The cause is something called upwelling. Steady southwest winds pushed the warm surface water away from shore, and to replace it, frigid water from deep in the lake rose up to take its place. Lake Superior is cold and deep, so there's always an icy reserve waiting just below the surface. Give the wind the right angle and it comes straight up to the top.
You can see it on the temperature map. The warmest water right now is tucked into Chequamegon Bay near Ashland, where the shallow, protected water holds its heat. But out around the islands and in the channels between them, it's a different story: that green tint threading through the Apostles is cold upwelling water, and it can turn frigid fast.
So if you're kayaking, paddleboarding, or thinking about a swim off the islands, expect water that can take your breath away, literally. Cold water that sudden is a real safety issue: it saps strength and triggers gasping fast, so wear your life jacket and know that "it was warm yesterday" means nothing on this lake.
Upwelling usually reverses once the winds shift, so the warmth will likely creep back in a few days. But this is a classic reminder of what makes Superior, Superior. It sets its own rules.