With the Met Office forecasting dry, fine and warm weather, the concern for households this week is not rain or pollen but the strength of the sun.
The Met Office says high pressure is bringing dry, fine and warm conditions, with hot sunshine developing across England and Wales and plenty of dry spells expected on Friday and through the weekend into the next week.
UV index set to hit high
According to forecaster Bigsalty, the UV index will reach 7 across much of the country, which sits in the high category on the official scale and is strong enough that the Met Office advises seeking shade during midday hours.
The Met Office UV forecast for London on Friday was set at 8, rated "very high", and on Saturday and Sunday it was "high" at 7. Going into the new week, it will again be 7 on Monday, dropping to 6 on Tuesday before bouncing back to 7 from Wednesday to Saturday.
Why drying outside can damage clothes
Clothing expert Christian Constantin, who runs Birmingham printing company OK T-Shirt, says anyone drying washing outdoors over the coming weeks should get into the habit of checking the UV forecast first, because of the damage this can do to clothes.
He said: "Everyone checks the weather before they hang washing out, but almost nobody checks the UV. It takes seconds to check, and it tells you whether your clothes are drying in gentle sunshine or getting blasted. Right now the index is at seven across much of the country, and that sun is strong enough to fade dyes and weaken fibres."
Constantin added: "I'm printing many shirts and items a day and when it comes to drying, I'm constantly doing it inside regardless if the sun is out. This is so there is zero UV intervention making the colours fade."
How the sun fades and weakens fabric
UV light breaks down the dye molecules in fabric, causing colours to bleach and fade. Dark and bright colours, including blacks, navies and reds, tend to show the damage first. The fading is often uneven, as the side facing the sun fades while the reverse does not, which can leave garments looking patchy or two tone.
Over repeated exposure, UV also weakens the fibres themselves, leaving fabric brittle and more likely to tear. Stretchy materials containing elastane, such as sportswear and swimwear, are particularly vulnerable and can lose their shape if regularly dried in direct sun. White synthetics can even yellow in strong sunlight, while printed designs may crack faster and elastic waistbands can perish more quickly.
When it is safest to dry outside
When UV levels are high, the safest windows are early morning and late afternoon, when the sun sits lower in the sky and its rays are weaker. The most damaging period is the middle of the day, roughly between 11am and 3pm, when the sun is at its strongest.
Washing hung out first thing will often be dry before the midday peak, while a late afternoon load avoids the harshest sun altogether and still benefits from the warmth of the day.
"If you can, get the washing out early and bring it in before lunchtime," Constantin said. "That first stretch of the morning dries clothes quickly and the sun is far gentler. It is the middle of the day that does the damage."
