Seasonal fatigue: Why you feel tired as winter ends

Dr Adit MathurAs winter slowly gives way to spring, a lot of people notice they just don’t feel like themselves. They’re more tired than usual. A little low on drive. Mentally foggy for no clear reason. What makes it confusing is that this slump shows up right when the days are getting longer and the weather is finally improving. You’d expect to feel better, not drained.

Most of the time, though, this isn’t a warning sign of illness. It’s simply your body adjusting to a change in season. That shift from winter to spring might seem subtle, but your system has been running on “winter settings” for months. Recognizing that can help you understand what’s normal and when it might actually be worth speaking to a doctor.

Why fatigue is common during seasonal change

Seasonal tiredness happens because your body responds to light and temperature more than you realize. During winter, when daylight hours are shorter, your internal body clock adjusts. You’re exposed to less natural light, and that affects how your brain regulates sleep and wake cycles.

So when spring rolls in and daylight stretches into the evening, your body has to recalibrate again. That adjustment period can leave you feeling off balance for a bit. It’s not dramatic, and it usually doesn’t last long. It’s just your system catching up to the new rhythm of longer, brighter days.
When the days start getting longer in spring, your body doesn’t instantly adjust. Your internal clock has been used to darker evenings and slower mornings for months. During that adjustment, you might feel sleepy during the day, low on energy, or just not as sharp as usual. It’s a bit like your body is running a step behind the season.

And then there’s the weather. Spring isn’t exactly steady. One minute it’s chilly in the morning, and by afternoon it feels almost warm. Those quick shifts can make your body work harder to maintain its balance. Constantly adapting to cooler and warmer temperatures can leave you feeling physically drained, even if you haven’t done much. It’s subtle, but it adds up.

The role of sleep disruption

During winter, a lot of people find themselves sleeping more hours, but that doesn’t always mean they’re sleeping well. With less daylight, your body’s rhythm shifts, and sleep can become lighter and more broken. You might spend more time in bed yet still wake up feeling like you didn’t fully rest.

Then spring arrives and the timing changes again. The sun rises earlier and sets later, and that extra light in the evening can quietly push your bedtime back. Even small shifts — going to bed 30 minutes later, waking up a bit earlier — can build up over days and weeks. Before you know it, you’re carrying a sleep deficit without realizing it.

And that lack of steady, good-quality sleep shows up in simple ways. You feel tired during the day. You’re more irritable than usual. Concentrating takes extra effort. Sleep disruption is one of the biggest — and most ignored — reasons people feel worn out during seasonal changes.

Vitamin D and winter depletion

Vitamin D levels commonly fall during winter due to reduced sun exposure. Low vitamin D is associated with fatigue, muscle aches, low mood, and reduced immunity.

While not all seasonal fatigue is due to vitamin D deficiency, it remains an important contributor, particularly in individuals who spend little time outdoors or have dietary limitations.

Clinical assessment is preferable to indiscriminate supplementation.

Reduced activity and metabolic slowdown

Cold weather often leads to reduced physical activity and subtle weight gain. This lowers cardiovascular fitness and insulin sensitivity, making everyday tasks feel more tiring.
As activity levels begin to rise again in spring, the body initially struggles to meet increased demand, resulting in perceived fatigue rather than increased energy.
Gradual reconditioning is more effective than sudden bursts of exercise.

When fatigue is normal

Seasonal fatigue is usually mild to moderate, fluctuates during the day, and improves with adequate sleep, hydration, sunlight exposure, and gentle activity.
Energy levels typically stabilise within a few weeks as circadian rhythms reset and activity patterns normalise.

Red flags that need medical evaluation

Fatigue should not be dismissed if it is

• Persistent beyond four to six weeks
• Progressively worsening
• Associated with breathlessness, chest discomfort, or palpitations
• Accompanied by unexplained weight loss or gain
• Linked to low mood, loss of interest, or sleep disturbance
• Associated with hair loss, cold intolerance, or menstrual irregularity

These features may indicate conditions such as anaemia, thyroid dysfunction, metabolic disorders, depression, or chronic inflammatory disease.

Practical steps to recover energy

Small, consistent adjustments are most effective during seasonal transitions.
Aim for regular sleep and wake times, even on weekends. Increase morning light exposure to reset circadian rhythm. Maintain hydration as temperatures rise. Resume physical activity gradually, prioritising walking and flexibility before high intensity workouts.
Balanced meals with adequate protein and micronutrients support energy metabolism and recovery.

The takeaway

Feeling tired as winter ends is common and usually temporary. It reflects the body’s effort to recalibrate to longer days, changing temperatures, and renewed activity.
However, persistent or disabling fatigue is not normal and should not be ignored. Recognising the difference allows early intervention and prevents unnecessary suffering.
Seasonal transitions test the body’s adaptability. With appropriate support, energy levels return and resilience improves.