Nothing ages the skin faster than the sun. People who spend much of their time exposed to it, from Australian sheep farmers to Californian ladies who lunch, have the prematurely wrinkled faces to prove it.
Excessive exposure to ultraviolet light causes sunburn, ageing and cataracts. As collagen in the skin is damaged the skin loses its elasticity.
A suntan is really evidence of skin damage. Each burn damages the skin a little bit more and if that damage continues year after year, the result is premature ageing. But a tan does offer some protection from the burning and ageing ultraviolet rays. Sunscreens also help.
Redheads and people with fair skins are more prone to suffer damage than those with darker skins. - JEREMY LAURANCE, HEALTH EDITOR
Water resources are hit in a heatwave by a double whammy: supply goes down just as demand goes up. Evaporation from foliage, the ground and water bodies increases, and aquatic plants themselves draw more heavily from the water they are growing in (such as rivers which may feed reservoirs); while consumer demand for water starts to soar. Demand for irrigation on farmland shoots up as well. Strong sunshine is bad for lakes and rivers, as the level of dissolved oxygen in the water drops, and breathing becomes difficult for fish; there is an increased possibility of "blooms" of toxic algae, which can be harmful to animals. - MICHAEL McCARTHY, ENVIRONMENT EDITOR
Stifling temperatures cause mere discomfort to most, but for some they can be lethal. The heatwave of August 2003 showed that hot weather can kill. There were more than 2,000 excess deaths in England, and 27,000 across continental Europe. Most of the victims were elderly who can be vulnerable to heat exhaustion. The experience of 2003 led the Government to issue a heatwave plan with four levels of alert. Measures include staying out of the sun, avoiding the outdoors from 11am to 3pm, wearing loose clothes and a hat, taking cool showers, and consuming cold food and water. - JEREMY LAURANCE
The long, hot days and sultry nights may result in a sexy, sun-kissed look but a heatwave appears to kill any passionate instincts among the British.
The birth rate declined to a record low of 657,000 in 1977, following the long hot summer of 1976. Couples who do kick their libidos into gear may be disappointed if their hearts are set on having a girl. Studies have shown that more boys than girls are conceived during a spell of hot weather. Scientists say the heat may have an effect on sperm because the female X-chromosome is more sensitive to heat. - MAXINE FRITH, SOCIAL AFFAIRS CORRESPONDENT
The sunny weather brings a downturn in work productivity. More than three-quarters of employees say hot working environments stifle their ability to get their jobs done. Eight out of 10 workers found it difficult to concentrate and two thirds admitted that normal tasks could take up to 25 per cent longer than usual in hot weather. More than half said they slacked off over the summer. - MAXINE FRITH
Every year about 50,000 people in Britain develop skin cancer - disfiguring lesions on the skin - though most can be successfully treated.
About 6,000 develop melanoma, the most serious form of skin cancer and about 1,500 of these die. Deaths from melanoma have doubled every 10 to 20 years in recent decades, reflecting Britons' love of the sun.
Severe sunburn, repeated year after year - especially before the age of 15 - is the biggest risk for melanoma. However, the highest incidence is among Scots who have never been abroad. Their fair skin puts them at risk even at home. - JEREMY LAURANCE
Every summer travellers fall prey to sweltering Tubes, train delays and over-heated roads. This week, temperatures could rise to 35.9C on the Underground, with Ken Livingstone, the Mayor of London, warning that there might be "serious loss of life" should a Tube train broke down inside a deep tunnel and people not have access to water.
Rail authorities above and below ground will have to impose harsh speed restrictions of 20mph if track temperatures near 100C - causing massive delays - for fear that lines and signal points will expand and buckle in the heat. London Underground fined the tube company Metronet £2.2m last month for failing to "pre-stress" (stretch) some Tube tracks to stop them buckling. Tarmac roads have been known to melt in hot weather. - OLIVER DUFF
Sunshine makes us happy and relaxed. Colours are brighter, the air is warmer, suntanned skin is more attractive and we feel better.
People in the sunnier climes of southern Europe and the Mediterranean tend to be more open, more expansive and more cheerful than their northern cousins. It is no accident that the best known image of despair - Munch's The Scream - was painted in Oslo.
At the scientific level, the action of light on the retina stimulates the production of brain chemicals that make us feel well.
The lack of sunlight in winter is thought to a cause a biochemical imbalance in the hypothalamus, a gland beneath the brain, which can trigger seasonal affective disorder. It is unknown in populations living within 30 degrees of the Equator - where the sun shines brightest. - JEREMY LAURANCE, HEALTH EDITOR
Beer and ice cream
Ice-cream makers are working round the clock. The Gloucester plant of Wall's is on 24-hour production to satisfy demand. "We are manufacturing at full capacity. We cannot get enough to the stores," a spokeswoman said.
Sales of suntan lotions are strong, too. Boots said it sold almost 750,000 bottles at the weekend - up 31 per cent on last year.
Brewers like nothing more than a football tournament or hot weather. The past month has been strong for the pub industry because it has combined both. A spokesman for the British Beer and Pub Association said bars would have sold an extra 15 million pints on the sweltering Saturday of England's World Cup match against Portugal. - MARTIN HICKMAN, CONSUMER AFFAIRS CORRESPONDENT
Dawn and sunset
Don't forget the added bonus: the dawns and sunsets. In a real heatwave, though the middle of the day may be scorching and too hot to do anything, the start and end can be magical. The early mornings have a still, sharp crystalline light which is peace itself, with a perfect temperature. The evenings are soft and sumptuous in temperature and also in colours, making the glass of wine and dinner in the open air something much more than just drinking and eating. And then, as you sit back, comes the great light crescendo of the setting sun. And it's all free. - MICHAEL MCCARTHY, ENVIRONMENT EDITOR
Holidays in UK
Hot weather often prompts UK holidaymakers to head for their own coasts rather than the airport. With many people having booked summer holidays in the winter, the number of foreign two-week summer holidays may not be substantially affected. However, many more people are expected to take weekend breaks in Britain and visit outdoor attractions. - MARTIN HICKMAN
Sunshine gives us butterflies. It is no coincidence that when it's a bright summer's day there are more about, adding to the general feeling of well-being with their bright flashes of colour. To generate enough energy to fly vigorously they have to absorb warmth from sunlight. Many have wings designed to soak up heat or to reflect the sun's rays on to their bodies. Of all the insects, it is the butterflies we are most grateful for. Here's a tip: go into an oak wood in southern England and you may see the silver-washed fritillary, the loveliest of them all. - MICHAEL MCCARTHY
The arrival of summer each year marks the point at which pale-faced Britons can replenish their depleted stocks of vitamin D, produced by the action of sunlight on the skin.
It is the only vitamin that humans make themselves and is essential for the health of skin and bones. But grey skies and short days from October to March mean 60 per cent of the population are deficient in it by the end of winter. - JEREMY LAURANCE
As the sun beats down, cricket and tennis are suddenly being played everywhere, and other energetic outdoor activities come into their own, from rowing and sailing to archery or even (God bless John Prescott for keeping the country laughing) croquet.
And outdoor activities can also be relaxing. Think picnics in the park, barbecues and the licensed madness of the music festival. - JESSIE KING