In northern climates, February has a particular heaviness. Even though we’ve passed the longest night of year, the days often feel darker, longer and more draining than December ever did. For society’s “night owls,” whose internal clocks naturally run later, this stretch of winter can be especially challenging.

As a biological anthropologist who studies sleep (and a night owl living in the North), I see this unfold every winter, and science offers a clear explanation for it.

The major reason can be found in our circadian system, the body’s internal 24-hour clock, which relies on morning light to stay aligned with the Earth’s day. After months of dim, delayed sunrises, that system is running low on the cues it needs to keep us alert and energized.

To understand this winter misalignment, it helps to look at our evolutionary history. Early human ancestors evolved near the equator, where sunrise and sunset are consistent throughout the year. In this stable environment, daylight serves as a reliable zeitgeber (German for “time giver”), synchronizing our internal clock to the external world.

But at higher latitudes, the light-dark cycle swings dramatically across seasons. Winter brings long nights, weak sunlight and more time indoors, and our internal clocks slowly drift later without that consistent morning light. Many people feel this misalignment as fatigue, irritability, low mood, difficulty waking or even difficulty falling asleep despite exhaustion.

These symptoms can intensify as winter progresses. Seasonal Affective Disorder, a seasonal pattern of depression, is more prevalent in northern regions.

February’s perfect storm

Our chronotype, or our biological preference for mornings (people known as “larks”) or evenings (night owls), can shape how strongly we feel these effects. It’s influenced by genetics, age and environment, and research has found that chronotype shifts later with increasing latitude. In other words, the farther north you live, the more likely you are to be a night owl.

This makes intuitive sense: when sunrise creeps toward 8 a.m., the body’s clock shifts later in response . The problem is that our social schedules don’t shift with it. School and work start times remain rigidly fixed, regardless of daylight hours.

In fact, our society is built around early chronotypes — it’s a lark-centred world — and these larks are often praised as disciplined or productive. In contrast, late chronotypes are often blamed for staying up late or struggling to wake on time.

But from an evolutionary perspective, chronotype variation may have been adaptive. The sentinel hypothesis proposes that having different chronotypes in a group staggers sleep and wake times across the night, thus helping early humans maintain vigilance against nighttime threats.

We all had our shift on the night watch — a built-in, rotating system of protection in our species. Yet in the modern world, the strengths of night owls (including increased openness and extraversion) are often overlooked.

What’s important to note is that late chronotypes aren’t choosing a different schedule. They are biologically tuned to a later rhythm. Forcing them into early mornings creates what researchers call social jet lag — the chronic mismatch between biological time and social time.

Social jet lag is strongly associated with increased caffeine use and alcohol use, higher rates of smoking and greater risk-taking behaviours. The chance of being overweight has been found to increase by 33 per cent for every hour of social jet lag.

February creates the perfect storm: while limited daylight affects everyone, late chronotypes face the added burden of social jet lag layered with this circadian misalignment. So what does this mean for health, and in particular, getting through the dark days of February?

Winter strategies for night owls

There are several practical, evidence-based strategies that can help align our circadian rhythms and reduce social jet lag during this last sprint of winter.

First, seek morning light, even if it’s weak. Morning light is the most powerful signal that synchronizes your circadian clock. If you can, get outside within the first hour of waking. If you can’t, use bright, indoor light strategically: bright light therapy in the first 30 minutes of waking can help shift the circadian clock earlier and improve mood.

In the afternoons and evenings, switch to using warm-toned bulbs instead. And avoid blue light from screens in the last hour before going to bed, as it’s a known suppressant of melatonin (the “darkness” hormone).

For late chronotypes, it’s important to keep a consistent schedule. While sleeping in on weekends can help recoup sleep loss, it also unfortunately increases social jet lag. Slowly shifting your bedtime on weekends earlier by around 10-15 minutes can more closely align free- and work-day rhythms.

It’s also critical to work with your biological rhythms, not against them. Try to structure your workday strategically: hold off on cognitively demanding tasks until late morning or early afternoon, when your circadian rhythm (and thus your alertness) is at its peak, and reserve early mornings for simpler tasks.

Lastly, emerging findings suggest that saunas may play a beneficial role in sleep health. Something to consider on cold, snowy days.

February may feel long, but it’s also the turning point; the slow return of light is already underway.

For those who naturally run on later schedules, remember that your chronotype is not a character flaw. Late chronotypes are more common for us northerners, shaped by our genetics and the environment around us. The goal shouldn’t be to force ourselves into someone else’s rhythm, but to find ways to live in better alignment with our own biology and the world we inhabit.