Hazards of Being Homeless
There are dangers homeless people face every day which most people don't usually experience. The death rate of homeless is about four times that of the general population. Some hazards are due to being pedestrians, having to live outdoors, poor nutrition and health care, and lacking protection from crime.
Vehicle vs. Pedistrian or Bicyclist Accidents
Homeless are often the victims of being hit by cars, either walking or on bicycle. The Tampa Bay area of Florida has the reputation of being number one in the US for pedestrian fatalities. I've had to jump out of the way of motorists several times, even though using crosswalks properly (and being extremely cautious), and then been yelled at for using the crosswalk (by possibly drunk drivers). Often people driving in a dangerous manner are so occupied with using cell phones that they aren't consious of what they are doing. I've observed that often emergency vehicles will not be given the right of way. Fire trucks with sirens, lights, and horns have to sit and wait until traffic will let them cross.
I've noticed that most people around here seldom walk anywhere, if they have an option. Two people I've known were killed by vehicles in the past couple years.
The San Francisco study indicated 9.6% of deaths were from accidents.
Assault, Robbery and Murder 
Living outdoors, without the benefit of locked doors, homeless are always at risk of being beaten, robbed, and possibly killed. Some people, often teenagers, will assault and even kill homeless just for entertainment. Every week there are stories across the country of homeless being severely beaten or killed, but these are only the ones that make it into the media. A good deal of the assaults go unreported. I've met several people that have been asssaulted, and have been myself, but these were never in the paper.
Denver, Colorado, has had the worst reputation for assaults on the homeless.
Homeless don't have the luxury of closing a door and locking out criminals.
A San Francisco study reported that 3.8% of homeless deaths were homicide.
Wild Animals
Some of the most common wild animals homeless may encounter are raccoons, rats, opposums, and feral cats (house cats turned wild). My primary concern with these is rabies. Raccoons get into everything looking for food. I've had to tie a suitcase, used for storing food, with wire since they learned to open the latches.
Alligators usually keep to themselves unless they've been fed by people, but three people were killed by alligators in one week in Florida (which is extremely unusual). One of those killed was a homeless woman in Pinellas County who may have fell asleep next to some water.
Bears looking for food, or feeling threatened, can be a serious problem (don't feed the bears!). Homeless people don't all just camp out in the inner city.
Weather
Nearly 100 people are killed and 500 injured annually in the US by lightning (NOAA). Being homeless makes finding shelter from the storms more difficult, so you do the best you can. I've been out in storms where the lightning was so close I could feel it in my chest, but had no-where to take cover.
With hurricanes, shelters open to everyone if a storm is imminent. It's one time those with homes learn what it's like in a shelter, together with the homeless. If the storm isn't classified as a hurricane the shelters don't  open, which means staying out in the weather even with up to 70mph winds, heavy rain, lightning, and tornados. Floods and flash-floods are number one in weather related deaths in the US.
Cold weather can be a serious danger, even in southern states. Every year many people die from hypothermia (even in Florida), or are seriously injured by frostbite. Cold weather is especially hazardous for those in poor health, as many homeless are. Some people use the term "freezing-to-death". If the weather is cold enough (even if well above freezing), you don't have adequate clothing or warm shelter, and your body cannot continue to maintain a normal tempertature, you will die. Freezing has nothing to do with it. 
Spiders, Snakes, and Biting Insects
There are about 7000 venomous snakebites annually in the US, of which 9 to 15 are fatal. Florida has black widow and brown recluse spiders (which may hide in clothing), among plenty of others. Wasps can be a serious hazard since they can give hundreds of bites to someone accidentally getting into a nest. Fire ants can be a problem as well, possibly giving hundreds of painful bites.
Aside from being annoying, mosquitoes can transmit diseases, and the West Nile Virus has been found in Florida and other states. While thought of as a disease found only in third-world countries, there were eight cases of locally-acquired malaria in Florida in 2003 according to the CDC.
Mosquito repellents containing DEET (such as Deep Woods Off) , picardin (Cutter Advanced Sport), or oil of lemon eucaliptus (Repel Lemon Eucalyptus) are effective. Many products called "herbal" are virtually worthless.
Medical Problems
Living outside, or being outdoors most of the time (even if spending nights in a shelter), results in being exposed to conditions leading to health problems that most people don't experience. Staying at crouded shelters increases the possibilities of contracting serious illnesses, such as tuberculosis.
Nutrition is a substantial problem among the homeless. Many free meals, which is all that some homeless eat, can amount to little more than carbohydrates (white rice, white bread, donuts, and pasta). Many homeless will avoid some free meals and shelters due to what is often a hostile, high-stress envionment.
Many soup kitchens are cutting back, or closing, due to lack of funds. Some are closed due to public pressure to eliminate the homeless (stop feeding them and they'll go away). Many homeless are fortunate to get one meal a day.
Bacterial skin infections (such as impetigo) and fungal infections can become serious problems without proper treatment. Living in crouded conditions in shelters can increase the transmission of diseases. If an infection is not treated quickly it can become life threatening.
Medical care is available for urgent life threatening or contagious problems, but some other serious problems may not qualify for any assistance.
www.homelessamerican.com                         HOMEPAGE
Overall
Of documented causes of death among the homeless, HIV/AIDS, substance abuse, heart disease, and cancer are the primary causes (generally in that order in city areas). In many cases, these were problems that resulted in these people becoming homeless, though some are a result of trying to cope with life in a hopeless situation. When people are told continually that there is no hope for them, they eventually accept it as their fate, and do whatever they can to ease the situation.
The hazards listed above are encountered by homeless people even if they don't have pre-existing substance abuse or health problems. These hazards, whether to health, quality of life, or staying alive, are what homeless people face every day simply by being homeless.