It’s never too early to start planning for one of Colorado’s seasonal, most anticipated natural phenomena.

It is indeed early to start planning for Medano Creek — the waterway that only appears for a brief period every year, curiously “surging” and sending small waves to the base of Great Sand Dunes National Park and Preserve.

The creek is the result of snowpack melting from the surrounding Sangre de Cristo mountains. Medano starts as “a trickle” sometime in April, reads a park webpage that regularly updates conditions.

Just how much the water swells and surges depends on snowpack. Midway through this month, that was measured at about 25% of average for the time of year after what the park called “a very dry winter.”

But “April is normally the second snowiest month of the year,” the conditions webpage noted, “so final snowpack and a more definitive flow forecast won’t be available until the end of April.”

By then, Medano Creek is typically a few inches deep. Flows increase into May, with the end of that month and early June known as the time for peak surges.

That’s when kids and kids at heart are seen wading in the water and riding waves on inflatables while others sit in lawn chairs and lay out blankets, and an unusual beach scene emerges at the foot of North America’s tallest sand dunes.

But with the peak flows of late May and early June comes a warning: “Weekends are extremely crowded, with long lines of traffic, overflowing parking lots, a crowded beach and full campgrounds,” reads the park webpage. “If possible, plan your visit on a weekday.”

And another warning: “As the creek becomes much lower and slower around the second week of June, mosquitoes will emerge in large numbers.”

The water is known to be even lower by late June. Mosquitos are known to disappear through July as the creek dries out.