Seasons in the Boundary Waters
For the canoeist in northern Minnesota, spring, summer, and fall are essentially crowded into a span of about five months May through September. The ice is usually off the lakes by the first week in May, but the trees aren't fully leafed out until at least the middle of the month. That period before the biting insects invade the North Country is an excellent time to explore the tiny creeks that may later be too low for easy navigation. But be prepared for weather cold enough to produce snow.
Early June is often a wet, cool, and gloomy time of year, usually plagued by hordes of mosquitoes, sand flies, and ticks. The fishing is best then.
July and early August normally offer the best weather for campers and the worst for anglers (too warm). As the summer progresses, the water levels of some shallow streams may become too low for navigating a loaded canoe, eliminating some excellent route possibilities.
From late August through September, after the first hard frost, biting insects have nearly disappeared and so have most visitors. This is a wonderful time to explore the wilderness, but you must be prepared for extended periods of cool and rainy weather, or even snow.
After September, contact local authorities for weather updates. It is not unusual to see the lakes ice over in October, and snow may accumulate on the ground.
Temperatures and rainfall vary, of course, throughout the BWCAW. The following statistics, recorded in International Falls, represent approximations for the western half of the Boundary Waters.
| | May | June | July | Aug. | Sept. |
| Avg. temp. | 51º | 60º | 66º | 63º | 53º |
| Avg. daily low | 38º | 48º | 53º | 51º | 41º |
| Avg. daily high | 63º | 72º | 78º | 76º | 64º |
| Precipitation | 2.6" | 3.9" | 3.5" | 3.6" | 2.9" |
|
Because of its close proximity to Lake Superior, the eastern part of the BWCAW sometimes exhibits extremely variable weather. While the lakes in the far eastern region may be blanketed with a cool, misty fog from Lake Superior, nearby lakes to the northwest may be enjoying warm sunshine, thanks to the subtle yet significant effect of the Laurentian Divide. Consequently, no weather data from any one reporting station can accurately represent all of the Boundary Waters.
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