Complex symptoms & the autonomic nervous system

Summer heat and the nervous system — why some people tolerate heat less well

Tino Both · 17 Jun 2026 · 9 min read

Briefly explained: Summer heat can worsen dizziness, exhaustion and palpitations because the body has to release heat while maintaining circulation. Bright light, prolonged standing and the perception of warmth can also shape the situation. Distinguishing these demands is more helpful than grouping everything under 'My circulation is weak'.

Do warm days repeatedly restrict your daily life?If your symptoms have been assessed medically and you want to understand better which situations remain particularly difficult, we can begin with a free initial telephone consultation. We discuss whether an additional functional perspective on perception, orientation and regulation in Vilshofen suits you.

Discuss your situation with warmth and summer heat →

Acute heat-related symptoms call for cooling and, where necessary, medical help first — rather than a functional test.

Others enjoy the summer day — you seek the nearest shade

A short shopping trip, a conversation while standing or crossing a sunny square: Suddenly your head feels heavy, you feel unsteady and need a break. Perhaps you have already had something to drink and have not exerted yourself much. Being told to 'just get used to the heat' is all the more unsatisfying.

It is worth looking more closely first: Do you mainly feel light-headed on standing up? Is direct sunlight much less comfortable than a warm room? Or do you feel overwhelmed even sitting down when brightness and many visual impressions are added? These distinctions give the conversation a direction.

Why heat can contribute to dizziness and exhaustion

In warm conditions, more blood is directed through the skin to release heat. Sweating supports cooling when the sweat evaporates. Fluid and salts are lost in the process. The heart and circulation have to respond to the changed conditions. Prolonged standing or additional physical effort in particular may then become harder.

High humidity makes evaporation more difficult. Direct sunlight adds heat to the body. Two days with similar air temperatures can therefore feel very different. The World Health Organization accordingly describes heat as a demand created by several interacting conditions — rather than only the number on the thermometer.

Heat tolerance is not a measure of willpowerExisting illnesses, medication, age, sleep and actual heat exposure influence how well someone copes. New or marked sensitivity to heat needs medical assessment. Please do not stop or change medication on your own.

Three different questions behind 'I cannot tolerate heat'

1. What happens to circulation?Light-headedness on standing up, near-fainting or an unusual racing heart directs attention towards circulation and changes of position. Medical findings and, where appropriate, blood pressure or pulse measurements matter here. A sensory exercise is no substitute.

2. What part do brightness and orientation play?Things are better in warm shade but become difficult in a bright square with people and movement. It is then also worth asking what light and visual processing contribute. Shade changes both radiant heat and brightness, however — this observation alone cannot yet separate the two.

3. How is a temperature stimulus perceived?Warmth is a sensory signal as well as a circulatory demand. Nerve endings in the skin respond to temperature. In my functional work, it can therefore also be interesting whether a mild, locally limited temperature stimulus changes the response during a predefined task.

These questions belong together but are not interchangeable. An assessment of gaze stabilisation does not answer a blood pressure question. A more comfortable skin stimulus does not yet tell us whether your body releases enough heat. This is precisely why my approach begins with your specific situation rather than a standard exercise against heat.

A specific insight: Assessing warmth information without heating the body

Nobody has to stand in the sun until symptoms appear for an appointment. We work in a comfortable environment when you feel stable. Following the conversation and necessary medical assessment, I choose a tolerable starting task, such as a small head turn while sitting. I may also use an indicator muscle that can be tested reliably and without pain.

A possible example: Is it the warmth — or the contact itself?I want to know whether a mild warmth signal at a selected area of skin changes the functional test response. Simply placing a warm object there and attributing every change to temperature would be imprecise. The object also touches the skin.

I therefore compare as similar a contact as possible without additional warming with comfortably warm contact. Site, duration and pressure remain as comparable as possible. Only then is the muscle response checked again. Pain, strong heating and large-area heat exposure are not part of this comparison.

The indicator muscle might respond stably to neutral contact but repeatedly hold less well with mild warmth information. I then initially pursue this specific stimulus question within my assessment system. If neutral contact itself changes the response, I must also consider touch information. Immediately assuming a purely 'warmth problem' would be premature.

From the unusual response to targeted integrationRepeat the stimulus: First, I check whether the observed difference repeats under comparable conditions.

Select additional input: Depending on the previous assessment, a gentle touch stimulus may be a possible addition, for example. I compare warmth information alone with warmth information plus the additional stimulus. I seek a combination in which the muscle holds stably again and which feels tolerable for you.

Integrate and assess again: The suitable combination is integrated within my method. The original stimulus situation then follows without the addition. We subsequently return to the agreed starting task: Has something also changed there in an understandable way?

The broad topic of 'heat' thus becomes a small, checkable question: Which information changes which response under these conditions? This is the part of my work that a general tip such as 'drink more' does not address. Drinking and protection from heat naturally remain important; the functional perspective begins with another question.

A good local retest is not yet clearance for a hot dayA mild skin stimulus and cooling the whole body are different demands. We therefore evaluate whether a selected approach helps in daily life through further tolerability and your actual everyday situations. Shade, breaks and protection from overheating remain necessary after a favourable test response too.

Would you like more than general heat tips?During the initial consultation, describe when warmth becomes difficult and what has been examined so far. From this, we can establish whether your remaining questions fit my Applied Neurofunction approach.

Talk about an individual perspective in Vilshofen →

What you can observe in daily life — without provoking symptoms

A brief note about situations that occur anyway is more helpful than a deliberate exertion test. Record whether you were sitting, standing or moving. Was it sunny or shaded, quiet or visually busy? Did cooling and rest make things better again? Where possible, distinguish light-headedness, swaying, a spinning sensation and general exhaustion.

After-effects also matter. If an activity has a marked lingering effect later or the next day, this belongs in the assessment. Particularly with pronounced activity intolerance, 'tolerate a little more every day' is not automatically a suitable recommendation.

What eases the load first in hot weather

Move demanding activities to cooler times of day and reduce your workload in heat. Seek shade or a cool room before you feel completely exhausted. Light clothing, cooling the skin and drinking regularly can help. If an illness requires you to restrict fluid intake, discuss your personal heat plan medically. Salt tablets or large quantities of electrolytes are not a universal solution.

With screen work or bright sunlight, more comfortable viewing conditions may also help: Less glare, a calmer background or appropriate sun protection. This does not replace cooling. Someone who becomes dizzy in heat should not continue training or drive to test whether they 'can manage again'.

When medical help is important

Suspected heatstroke: 112Confusion, impaired consciousness, seizures, collapse or rapid severe deterioration after heat exposure are emergency signs. Call for help immediately and move the person to cooler surroundings and cool them until emergency services arrive. Do not leave them alone. Give nothing to drink if consciousness is impaired. Heavy sweating does not rule out heatstroke either.

For dizziness, nausea and marked weakness, stop the activity, cool down and rest. Seek medical help if symptoms do not improve clearly and quickly, are severe or recur. New persistent heat sensitivity, near-fainting or an unusual racing heart should also be discussed medically independently of one hot day. Information about heat illness is provided by the NHS and the CDC.

Frequently asked questions about summer heat and the nervous system

Why do I become dizzy in heat despite drinking enough?Drinking is only one part of adaptation. Skin blood flow, circulation, physical effort and other health factors may contribute. Persistent or recurring dizziness should therefore not be explained by fluid loss alone.

Why is direct sunlight worse than warm air?Sunlight adds radiant heat and strong brightness. This can increase both heat exposure and visual discomfort. Temperature alone does not show which demand is central for you.

Can heat sensitivity be assessed functionally?Individual tasks involved can be considered, such as gaze stabilisation or the response to a mild temperature stimulus. In my work, I select these assessments according to the history. A local temperature comparison does not measure how well your body can dissipate great heat.

Do I have to push through symptoms to get used to heat?No. Dizziness, marked weakness or nausea are not training goals. Any adaptation to warmth must suit health and tolerance; unclear symptoms call for assessment first.

Take heat seriously — and still look more closely

'I feel unwell in warmth' can be the beginning of a precise question. Perhaps circulation is central. Perhaps an already difficult visual task becomes more demanding in summer conditions. Perhaps an additional look at temperature perception is useful. In Applied Neurofunction, my aim is to keep these possibilities distinct and derive an understandable next step from your observations.