By Jane Elliott
Health reporter, BBC News
The alert tells patients when cold weather is due
A scheme warning people with a lung condition about weather which could have an effect on them has cut hospital admissions for the problem by a fifth.
The Met Office alerts tell people with chronic obstructive pulmonary disease (COPD) when cold weather is due.
More than 8,000 patients from 189 GP practices across the UK are signed up to the scheme.
The British Lung Foundation says users can plan to avoid being out during cold snaps which could harm their health.
COPD is a progressive lung disease that affects over 900,000 people in the UK, causing acute breathlessness meaning everyday life can be very difficult.
Cold air can worsen symptoms by making airways narrower, making it even harder to breathe. Chest infections are also more common in winter.
Deaths due to respiratory disease, like COPD, increase 12 days after a fall in temperature, which causes an increase in colds and breathing problems.
Compared to winter 2006 - when the scheme was not running - NHS figures show there was a 24% fall in hospital admissions for COPD patients from the practices in the scheme, but there was just a 3% drop seen in practices in the same areas which are not taking part, giving a 21% net benefit.
Each GP practice involved in the scheme is e-mailed a weekly forecast between November and April.
The Met Office uses health information, such as what respiratory viruses are circulating, as well as weather forecasts to decide when warnings need to be given.
If an alert is needed, patients receive an automated phone call spelling out what they can do to safeguard their health and asking if they feel they need to see their GP.
There were four alert calls during last winter.
Wayne Elliott, the head of the Met Office forecasting team, said: "If there is a cold snap coming, patients can get their shopping in beforehand, or contact their doctors and get their prescription early so they are not exposed to the low temperatures."
The Met Office has surveyed more than 3,000 of the patients taking part in the scheme.
Over a third were prompted to contact their GP practice to get a repeat prescription for their medication, while 11% consulted their doctor about worsening symptoms.
Patients commented that the service "made them feel that someone cared".
One patient said: "I found this system to be very useful in planning and ordering of medication, and adjusting lifestyle to take account of the weather conditions."
Dame Helena Shovelton, chief executive of the British Lung Foundation (BLF) said the forecast was "of great benefit".
"Being aware of detrimental weather conditions enables people to plan ahead and avoid situations that could aggravate their condition."
But Dame Helena said being part of the scheme should not make patients complacent about their condition.
"It should not be seen as a replacement for other important services, such as pulmonary rehabilitation classes, which increase lung fitness, and specialist respiratory nurses which play a vital role in keeping people with COPD healthy and out of hospital - although access to them is patchy across the UK."