In fact, self-reported rates of respiratory diseases (including asthma, chronic bronchitis and emphysema) are double that of the general population.The homeless population often live in higher risk urban areas, with increased exposure and little protection from the elements. They also have limited access to clean drinking water, and other methods of cooling down. The built environment in urban areas also contributes to the "heat island effect", the phenomenon whereby cities experience higher temperatures due to the predominance of dark, paved surfaces, and lack of vegetation. Homeless populations are often excluded from disaster planning efforts, further increasing their vulnerability when these events occur. Without the means to escape extreme temperatures and seek proper shelter, and cooling or warming resources, homeless people are often left to suffer the brunt of the extreme weather. The health effects that result from extreme weather include exacerbation of chronic diseases and acute illnesses. Pre-existing conditions can be greatly exacerbated by extreme heat and cold, including cardiovascular, respiratory, skin and renal disease, often resulting in higher morbidity and mortality during extreme weather. Acute conditions such as sunburn, dehydration, heat stroke, and allergic reactions are also common. In addition, a rise in insect bites can lead to vector-borne infections. Mental health conditions can also be impacted by extreme weather events as a result of lack of sleep, increased alcohol consumption, reduced access to resources and reduced ability to adjust to the environmental changes. In fact, pre-existing psychiatric illness has been shown to triple the risk of death from extreme heat.
A national service, called Streetlink, was established in 2012 to help members of the public obtain near-immediate assistance for specific rough sleepers, with the support of the Government (as housing is a devolved matter, the service currently only extends to England). The annual number of homeless households in England peaked in 2003–04 at 135,420 before falling to a low of 40,020 in 2009–10. In 2017–18, there were 56,600 homeless households, which was 60 per cent below the 2003–04 peak, and 40 per cent higher than the 2009–10 low. The UK has more than 120,000 children in temporary accommodation, a number which has increased from 69,050 children in 2010.In 2007 the official figures for England were that an average of 498 people slept rough each night, with 248 of those in London.Homelessness in England since 2010 has been rising. By 2016 it is estimated the numbers sleeping rough had more than doubled since 2010. The National Audit Office say in relation to homelessness in England 2010–17 there has been a 60% rise in households living in temporary accommodation and a rise of 134% in rough sleepers. It is estimated 4,751 people bedded down outside overnight in England in 2017, up 15% on previous year.