Dressing for Heat, Sun and Humidity
Hot-weather equipment is not simply summer clothing.
A dry desert at 40°C, a humid tropical forest at 30°C and a sun-drenched glacier at altitude may all be described as “hot”, yet each creates a very different problem for the human body.
The challenge is to balance five competing requirements:
heat loss, moisture management, protection from ultraviolet radiation, protection from the environment and protection from insects.
That balance has changed considerably as outdoor clothing technology has developed.
Modern fabrics can provide substantial ultraviolet protection, manage moisture, dry rapidly and, in some cases, incorporate insect-repellent treatments. At the same time, there has been a welcome rediscovery of a principle that travellers in hot climates have understood for centuries:
Sometimes covering more of the body keeps you more comfortable than exposing it.
Hot and Dry Versus Hot and Humid
Before choosing clothing it is important to distinguish between two fundamentally different environments.
Hot and dry
In low humidity, perspiration evaporates readily.
This makes evaporative cooling extremely effective.
Loose clothing can trap a small layer of air around the body while still allowing sweat to evaporate. Long sleeves and trousers also reduce the amount of solar radiation reaching the skin.
This is why traditional desert clothing commonly covers most of the body rather than exposing it.
Interestingly, cotton is not automatically a poor choice in these conditions. Because cotton retains moisture, damp cotton can provide useful evaporative cooling in extremely hot, dry environments. Modern outdoor guidance still recognises this exception to the familiar “cotton kills” rule. (REI)
The disadvantage appears when temperatures fall or the environment becomes damp: wet cotton dries slowly and can become a liability.
Hot and humid
High humidity presents almost the opposite problem.
The atmosphere is already carrying substantial moisture, so perspiration cannot evaporate efficiently.
The objective therefore shifts towards:
- maximising airflow;
- minimising unnecessary insulation;
- moving moisture away from the skin;
- drying clothing rapidly;
- reducing chafing;
- and preventing fungal and bacterial skin problems.
Loose-fitting lightweight nylon, polyester and modern blended fabrics are generally much more practical here than heavy cotton. Merino can also be useful because of its moisture management and resistance to odour, although very lightweight synthetics generally dry faster. (REI)
Fabrics and Sun Protection
One of the greatest changes in outdoor clothing has been the widespread adoption of the Ultraviolet Protection Factor — UPF.
The older variety of national clothing-protection systems has largely given way in consumer outdoor clothing to UPF terminology.
UPF describes how effectively a fabric limits ultraviolet radiation passing through it.
A garment rated UPF 50, for example, permits only a small fraction of incident UV radiation to pass through the tested fabric.
For prolonged exposure, UPF 40–50+ clothing is now readily available.
The usefulness of sun-protective clothing should not be underestimated. Unlike sunscreen, fabric cannot be accidentally rubbed off, inadequately applied or forgotten on one shoulder.
Modern garments may obtain their protection through the density and construction of the fabric itself rather than through a chemical treatment.
A good example is the current Patagonia Capilene Cool Sun Hoody. It uses a lightweight recycled polyester construction, provides UPF 40+ protection and is designed to wick and dry rapidly. (Patagonia)
That represents a considerable evolution from the traditional expedition shirt.
Shirts
The classic hot-weather expedition shirt remains a remarkably effective design.
Its features generally include:
- long sleeves;
- loose fit;
- high or turn-up collar;
- back ventilation;
- rapid-drying fabric;
- chest pockets;
- sleeve-retaining tabs;
- and substantial UV protection.
Long sleeves can actually be preferable to a T-shirt under fierce sun because they reduce direct solar heating and reduce the amount of sunscreen required.
The modern expedition shirt
Modern versions increasingly combine UV protection with moisture management and insect resistance.
The current Craghoppers NosiLife Adventure Long-Sleeved Shirt, for example, combines lightweight ripstop construction, a vented back, roll-up sleeves, a neck-protecting collar, moisture management and UPF 50+ fabric with built-in insect-repellent technology. (Craghoppers)
That makes this style particularly suitable for:
- tropical travel;
- safari;
- humid trekking;
- areas with biting insects;
- and general expedition use.
The modern sun hoody
Another increasingly popular alternative is the sun hoody.
Instead of the traditional button-front expedition shirt, this is essentially an extremely lightweight long-sleeved technical base layer with an integrated hood.
The hood protects the ears, neck and sides of the face, while the fabric protects the arms and torso.
The Patagonia Capilene Cool Sun Hoody is a current example, offering UPF 40+ protection with lightweight, fast-drying polyester. (Patagonia)
For exposed trekking, climbing, paddling and glacier travel this can be extraordinarily effective.
The traditional shirt remains superior where pockets, ventilation and insect protection are priorities.
The sun hoody wins where simplicity, movement and continuous UV protection matter most.
Patagonia Men’s Cap Cool Sun Hoody
£90.00
Columbia Men’s Tamiami II Long-Sleeve Shirt
£56.57
Craghoppers Kiwi II Short Sleeve Shirt
£25.00
Trousers
Hot-weather trousers have changed substantially.
Traditional lightweight trekking trousers were often relatively loose nylon garments. Modern examples increasingly use combinations of:
- nylon;
- elastane;
- ripstop;
- articulated knees;
- mechanical stretch;
- ventilating zips;
- reinforced wear areas;
- and durable water-repellent treatments.
The fundamental principle remains sensible:
the trousers should be light enough to wear in heat but tough enough for the environment.
Long trousers offer significant advantages over shorts in many environments.
They protect against:
sun,
vegetation,
abrasion,
ticks,
mosquitoes,
sand,
and cultural difficulties associated with exposing the legs.
Convertible trousers
Zip-off trousers remain available and still make sense for general trekking and travel.
Their greatest advantage is versatility.
Their disadvantages are the additional zips, seams and bulk around the thighs.
Modern stretch trousers have consequently reduced their popularity among serious walkers.
A modern technical alternative
The current Montane Terra is a useful illustration.
It uses lightweight TACTEL nylon with CORDURA ripstop reinforcement at wear points, has mesh-lined thigh vents and dries quickly. The current UK retail price is £85. (Montane – UK)
Rather than removing the lower legs entirely, opening the thigh vents allows considerably more airflow while maintaining protection from sun and vegetation.
Montane also still offers a convertible Terra version for those who prefer the traditional zip-off concept. (Montane – UK)
This illustrates the modern choice quite well:
zip-off trousers maximise versatility; vented stretch trousers maximise performance.
Head Protection
A hat remains one of the simplest and most effective pieces of hot-weather equipment.
A baseball cap protects the scalp and part of the face but provides relatively poor protection for the ears and neck.
A proper sun hat should have a sufficiently broad brim to shade:
the forehead,
ears,
sides of the face,
and ideally part of the neck.
Ventilation is equally important.
Modern sun hats combine lightweight nylon, mesh ventilation, moisture management and high UPF ratings.
The Outdoor Research Sunbriolet is a good example. Its current design uses lightweight quick-drying nylon, zoned ventilation and UPF 50+ fabric, with a brim of approximately 3.3 inches at the front and 4.1 inches at the rear. (Outdoor Research)
For very exposed mountain or desert conditions, a legionnaire-style cap with an integrated neck flap remains extremely effective.
Outdoor Research Helios Sun Hat
£33.30
Outdoor Research Sun Bucket
£25.90
UPF 50+ Baseball Cap & Neck Gaiter
£24.00
Neck Protection: From Shemagh to Technical Gaiter
The shemagh remains an extraordinarily effective item of desert equipment.
A large cotton cloth can provide:
sun protection,
dust protection,
neck protection,
limited evaporative cooling,
and emergency utility.
The basic design needs very little technological improvement.
However, modern technical neck gaiters provide a lighter alternative.
These are commonly made from polyester or merino blends and can be worn as:
a neck covering,
face covering,
headband,
head covering,
or under a helmet.
In extremely dry desert conditions, traditional cotton can still be useful because deliberately wetting it produces evaporative cooling.
For high-output activities such as trail running or mountaineering, modern synthetic gaiters generally dry considerably more quickly.
Waterproofs in Tropical Heat
This is one area where physics remains stubbornly resistant to marketing.
A waterproof-breathable membrane works because water vapour moves across a gradient.
In warm, saturated tropical air, that gradient becomes extremely small.
Add heavy exertion and the wearer can easily generate moisture faster than the garment can transport it.
Even modern waterproof shells can therefore become intensely uncomfortable in tropical humidity. Contemporary outdoor guidance continues to acknowledge that waterproof-breathable shells struggle as humidity and exertion increase. (REI)
For prolonged tropical rain, the humble poncho retains several advantages:
- excellent ventilation;
- rapid deployment;
- coverage over clothing;
- potential coverage over part of a rucksack;
- simplicity;
- low cost.
Its weaknesses are equally obvious:
wind,
vegetation,
climbing,
and scrambling.
A poncho blowing around on technical terrain can become a nuisance or hazard.
For jungle tracks it can be excellent.
For exposed mountain terrain a properly fitted shell normally remains preferable.
An umbrella also deserves more respect than outdoor fashion sometimes affords it.
In non-technical terrain an umbrella creates its own portable shade, provides excellent ventilation and keeps heavy tropical rain completely away from the upper body.
Footwear
Hot-weather footwear has arguably changed more than almost any other category.
Heavy leather boots are no longer the default answer for trekking.
Modern trail shoes and lightweight boots use:
mesh,
synthetic fabrics,
high-friction rubber,
lightweight cushioning foams,
and highly developed sole geometries.
For many hot-weather routes, a lightweight non-waterproof trail shoe may now be more comfortable than a traditional boot.
The waterproof-membrane question
Waterproof membranes such as Gore-Tex are excellent when the objective is preventing external water reaching the foot.
They become less useful when water is inevitably going to enter from above.
This distinction is particularly important in jungle environments and repeated river crossings.
Once a waterproof boot fills with water, drainage and drying become difficult.
A highly ventilated, non-waterproof shoe can become wet almost immediately—but it can also drain and begin drying immediately.
That is essentially the same principle behind the traditional jungle boot.
Traditional jungle boots remain available.
Wellco Jungle Boots
£39.99
US Type Jungle Boots
£55.00
However, for many modern travellers and trekkers, breathable trail-running footwear represents a much more comfortable alternative.
The decision should therefore be environmental rather than ideological:
Keep water out where practical. Let it escape where getting wet is inevitable.
Socks and Foot Care
Cotton socks remain a poor choice for sustained trekking.
They absorb substantial moisture, dry slowly and can contribute to maceration and friction.
Modern alternatives include:
synthetic fibres,
merino wool,
or blends of the two.
Merino has the advantage of excellent odour resistance and temperature regulation.
Synthetic socks tend to dry faster.
Neither choice eliminates blisters automatically.
Fit, moisture, friction, footwear and individual foot anatomy remain more important than the fibre name on the packet.
In persistently wet environments, foot care becomes a deliberate daily task.
Feet should be cleaned, inspected and allowed to dry whenever possible.
Glacial Heat
One of the great misconceptions of high mountains is that altitude automatically means cold.
A still glacier under intense sunshine can be extraordinarily hot.
Three things occur simultaneously:
direct solar radiation,
reflection from snow and ice,
and increased ultraviolet exposure at altitude.
Snow can also reflect UV upwards into areas that normally receive relatively little direct sunlight.
The underside of the nose, lips, ears and underside of the chin can therefore burn surprisingly easily.
Modern mountaineering clothing makes managing this much easier.
A typical high-exposure system might consist of:
a lightweight UPF long-sleeved top,
sun hoody,
cap or helmet-compatible sun protection,
category-appropriate sunglasses or glacier glasses,
lightweight softshell trousers,
and SPF 50+ sunscreen on exposed skin.
Early starts are still important, but not simply because of heat. Snow bridges, glacier surfaces and objective hazards can change substantially as temperatures rise.
Sunscreen: What Has Changed
Sun protection advice has changed considerably.
The old idea that SPF simply tells you how many times longer you can remain in the sun is potentially misleading because real-world protection depends heavily on application quantity, sweating, rubbing, water exposure and UV intensity.
Current NHS guidance recommends choosing sunscreen with:
at least SPF 30 for UVB protection and at least four-star UVA protection.
SPF ratings now extend to 50+. (nhs.uk)
For prolonged outdoor activity, SPF 50 or 50+ is an entirely reasonable choice.
The NHS also emphasises something more important than increasingly large SPF numbers:
people generally do not apply enough sunscreen.
For an adult covering the whole body, NHS guidance gives approximately six to eight teaspoons as a guide. Sunscreen should be reapplied frequently and after swimming, heavy sweating or towel drying. (nhs.uk)
Cancer Research UK also emphasises that UV strength cannot be judged by temperature. UV can be damaging even when the weather does not feel particularly hot, and checking the UV index is more useful than judging the air temperature. (Cancer Research UK – Cancer News)
La Roche-Posay Anthelios UVMune 400 Pro Sport SPF50+
£15.75
Garnier Ambre Solaire Sensitive Advanced SPF50+
£7.99
For outdoor use I would favour SPF 50+, broad-spectrum/UVA protection, sweat or water resistance and a formulation you are actually willing to reapply.
The theoretically perfect sunscreen is of little value sitting unused in a rucksack.
Repelling Insects
This area has also moved forward substantially.
Mosquitoes should not simply be regarded as an irritation.
Depending on location they can transmit:
malaria,
dengue,
yellow fever,
chikungunya,
Zika,
Japanese encephalitis,
and other infections.
Protection therefore involves several layers.
Clothing
Long sleeves and trousers reduce exposed skin.
Loose clothing is preferable because mosquitoes may be able to bite through very thin fabric held tightly against the skin.
Treated garments provide an additional defence.
Modern travel clothing such as the Craghoppers NosiLife range incorporates insect-repellent technology alongside sun protection and moisture management. (Craghoppers)
DEET
DEET remains one of the most important repellents.
Current UK travel-health guidance recommends 50% DEET for travellers where significant insect-borne disease is a concern. Importantly, increasing the concentration above 50% does not provide a corresponding increase in duration of protection. (TravelHealthPro)
One disadvantage is that DEET can damage certain plastics and synthetic materials.
Care is therefore required around:
sunglasses,
watch straps,
camera equipment,
and some technical clothing.
Picaridin/Icaridin
Picaridin—also known as icaridin—is now a major alternative.
TravelHealthPro states that approximately 20% icaridin can provide protection comparable with DEET at appropriate concentrations and recommends at least 20% where protection against malaria-transmitting mosquitoes is required. (TravelHealthPro)
It also avoids some of DEET’s unpleasant effects on plastics.
Repellent and sunscreen
Where both are required:
sunscreen goes on first, insect repellent afterwards.
This is specifically reflected in current UK travel-health guidance. (TravelHealthPro)
Jungle Formula Extra Strong Insect Repellent
£20.14
PARA’KITO Family Mosquito Spray
£9.95
The Modern Hot-Weather System
Rather than thinking about individual garments, it is useful to consider a complete system.
| Environment | Shirt/top | Legwear | Footwear | Head | Additional protection |
| Dry desert | Loose long-sleeved UPF shirt or sun hoody | Lightweight long trousers | Ventilated trail shoe/boot | Wide-brim hat/shemagh | SPF 50+, sunglasses |
| Humid tropics | Fast-drying vented shirt | Lightweight ripstop trousers | Rapid-draining non-waterproof footwear | Ventilated brimmed hat | Insect repellent, head net |
| Safari/travel | UPF/insect-treated shirt | Lightweight travel trousers | Lightweight walking shoe | Brimmed hat | SPF 50+, repellent |
| Hot mountain approach | Sun hoody or technical synthetic | Stretch trekking trousers | Trail shoe/light boot | Cap/hat | SPF 50+, sunglasses |
| Glacier/high altitude | UPF technical layer | Lightweight mountain trousers | Appropriate mountain boot | Cap/helmet protection | Glacier glasses, SPF 50+ |
| Monsoon/jungle | Fast-drying long sleeves | Ripstop trousers | Drainable footwear | Brimmed hat | Poncho, dry bags, repellent |
What Has Really Changed?
Outdoor clothing has become lighter, faster drying and far more specialised.
UPF-rated fabrics are commonplace.
Insect-resistant clothing is readily available.
Sun hoodies have emerged as a distinct category.
Trail shoes increasingly replace boots where ankle protection and extreme load carriage are unnecessary.
Picaridin provides a genuine alternative to DEET.
Modern sunscreens offer sophisticated UVA and UVB protection.
Yet many of the principles remain surprisingly old-fashioned.
Cover the skin.
Create shade.
Allow air to circulate.
Keep insects away.
Choose clothing that suits the climate rather than simply the temperature.
And recognise that the most technologically advanced garment available is useless if the underlying design is inappropriate for the environment.
The objective of hot-weather clothing is not simply to wear as little as possible.
It is to create a controllable microclimate between the body and the environment.
That principle works whether you are crossing a desert, moving through tropical forest or standing on a glacier at 4,000 metres.
