Why Do My Mood and Health Crash Every Time the Seasons Change?
Most people notice it: every time the seasons shift, mood swings and minor health issues tend to follow. For those with a weaker baseline health, seasonal transitions can bring on real gloom, irritability, and a full health crash.
So what’s actually causing this?
During a seasonal transition, temperatures shift significantly — gradually rising, as in the move from winter to spring, or spring to summer; or gradually falling, as in the move from summer to fall, or fall to winter.
When temperatures rise: as the environment warms up, your body cuts back on energy production. It no longer needs to generate as much energy to maintain that stable 37°C (98.6°F) internal temperature, so that portion of energy is no longer necessary — and gets cut. As a result, your body’s total energy output drops.
So what happens once that “unlocked” energy total goes down? If you keep the same activity level as before, the share of energy allocated to your immune system drops right along with it. That makes your body more vulnerable to infection and illness.
Hospital data consistently shows a sharp rise in flu admissions during seasonal transitions — in some cases, admissions have doubled compared to the months before, according to pediatric hospital records tracking flu cases through these transition periods.
A drop in total energy also brings mood changes with it. With less energy available, you become more prone to sadness, anxiety, and fear. If you’ve read the article “Why Does Fall Weather Feel So Pleasant, Yet Leave Me Exhausted and Quietly Sad?”, you’ll already understand this: sadness is really just the expression of an energy shortfall, while happiness is the expression of an energy surplus.
And if you’ve read Demystifying Anxiety, Fear, and Anger, you also know that lower energy levels make it far easier for anxiety and fear to get triggered.
In short: seasonal transitions reduce your body’s total unlocked energy, which makes you more prone to sadness, anxiety, and fear than usual. People with a stable baseline of health tend to get through this stretch fairly easily. But for those with a weaker baseline — often people already dealing with a physical or psychological condition — the energy drop can be too much to absorb, and both their mood and their health collapse together.
When temperatures fall: as the environment cools down, your body generates more energy to make up the difference. But if the temperature drops too fast, too suddenly, your body’s ability to adapt can’t keep pace — meaning the extra energy it produces isn’t enough to cover the drop, forcing it to pull from your body’s overall energy reserves instead. That leaves less energy for daily activity and for your immune system. If you keep the same routine as before, you end up running an energy deficit — and the result is the same: more sadness, more anxiety, more fear. If your baseline health is already weak, this makes you even more prone to getting sick and to a mood crash.
How to Avoid a Mood and Health Crash During Seasonal Transitions
Immediate fix: The moment you notice your body reacting to the seasonal shift — fatigue, unusual warmth, mood swings, a runny or stuffy nose — apply these right away:
Rest more, work less. Instead of keeping your usual pace, scale back your workload and rest more — for example, sitting or lying down with your eyes closed for 30 to 60 minutes. Giving your body time to generate enough energy to compensate helps you avoid getting sick.
Regulate your temperature. If it’s turning cold, dress warmly to reduce the energy your body has to spend on generating heat, freeing that energy up for your immune system instead. If it’s getting hot, use air conditioning to help your body stay cool.
Long-term fix:
To stop every seasonal transition from feeling like an ordeal, work on raising your body’s baseline energy level: exercise or play sports regularly, at least 3 times a week. Over time, this raises your overall energy baseline.
When a seasonal transition hits, ease off your training for a bit — take 1 to 2 weeks off. The extra energy you’re not spending on exercise goes toward keeping your mood stable and protecting your health during this sensitive window.
In short, your body always needs a certain amount of energy to keep your temperature stable, support your immune system, and keep your mood balanced. Every seasonal transition — whether temperatures rise or fall — forces your body to reallocate that energy, and during that adjustment period, the share going to your immune system and your emotional balance is usually the first to get cut. That’s why you’re more prone to fatigue, sadness, anxiety, and even illness whenever the seasons change — not because your body is weak, but because it’s going through a completely natural adaptation process. Once you understand this, instead of forcing yourself to keep the same pace, you can rest more, regulate your temperature at the right moments, and build a stronger baseline of health ahead of time — so that each time the seasons change, your body has enough energy “in reserve” to get through it more gently.