April may well be the cruellest month, as British poet T.S. Eliot wrote, especially for runners. When spring feels more like winter and the temperature is fluctuating wildly from day to day, how do you know when to put away the base layer and break out the shorts?
You don’t have to be a meteorologist to quickly learn what works best in different conditions (but it helps).
A great rule of thumb is to dress as if it’s 15 degrees warmer than what the thermometer reads, and as if you’re going out for a leisurely walk rather than a run. (Though if you’re like me, deciding how to dress for normal life is not much easier than it is for a run.)
Your most useful piece of gear might be an outdoor thermometer, mounted where you can see it from inside your cozy kitchen. With practice, you can train yourself to know what to put on at different temperatures. (You could even mark up your thermometer with a sticky note reading “shorts/tights” once you figure out your personal threshold. More on that in a minute.)
How will I know if it’s warm enough?
Temperature is not the only consideration, however. Is it windy? Running into a headwind will feel colder than the air temperature. Similarly, rain or snow will usually make you feel cooler than clear weather. What to wear also depends on how hard or easy you’ll be running. If you’re doing track intervals or a tempo run you’ll work up a sweat sooner, with overheating more likely–which makes it a good time to test out lighter clothing options. (A long run may be more problematic if you get the clothing choice wrong.)
We recommend trying the switch at around 10 C. If you’re usually cold or have a very light build, you could wait til it’s slightly warmer, and vice versa. You’ll quickly find out if it’s too soon. Or the relief you feel will indicate you could have ditched the tights at 7 C, or even cooler.
What about racing?
When competing at races, it’s best to err on the side of under- rather than over-dressing, even if it’s uncomfortably chilly on the start line. (Having to remove your jacket and tie it around your waist will definitely cost you time. If necessary, bring a throwaway top layer you can chuck to the side of the road once you heat up. At larger races there are volunteers to collect and donate discarded clothing.) Assuming you’re not an elite runner, don’t feel you have to copy the singlet-and-shorts-in-all-conditions custom, especially if you can see your breath!
I try not to pay too much mind when I see other runners whose clothing choices differ from mine. Selecting appropriate gear for conditions is obviously very personal. And conditions can change while you’re out there, especially on a very long run. You won’t nail it every time. But with practice, you can get a very good feel for how to be as comfortable as possible, so you can get the most out of your training.