They say March comes in like a lion and goes out like a lamb.

“They” are wrong.

All of spring is more like a monkey, from beginning to end—unpredictable, mischievous, always ready with a trick. And what I’ve found is that my energy levels fluctuate right along with the changing weather: rising when it’s warm, falling when it’s gloomy or stormy.

My kids, on the other hand, get energized when it’s chilly and damp but wilt in the warmth (so much for sharing my genes!).

For any of us, allowing the weather to dictate how much we exercise is a slick slope into not exercising much at all. And the key to avoiding this fate is the ever-handy Boy Scout motto: Be prepared.

It starts with scheduling: Instead of leaving your workouts to a whim, carve out time for them. Input them in your calendar, and treat them as if they were work appointments, regardless of how you feel when the time arrives.

Then, as any good event planner would, make a weather-contingency plan. If you’re planning a walk or run outdoors, select ahead of time which workout video you’ll do in your family room if the weather is not to your liking. Or maybe the forecast isn’t conducive to you getting to the gym at lunch like you planned, so you can execute your Plan B of walking your building stairwell. Or commit to an exercise circuit while you watch Dancing with the Stars that evening.

The “Mankind versus Nature” conflict has been raging for millennia. Don’t be another of its victims. Make a fitness plan and stick to it, regardless of what the weather monkey throws at you.