Allergens are all around us, gunning to make us sneeze, our eyes itch and make us feel just plain miserable. At some point during the year, an estimated 50 to 60 million people in the U.S. - - around 20 percent of the population - - struggle with allergies. What are the worst seasons for allergies in the U.S.?

The answer to that question depends on the person and where they live. What may not affect one person`s allergies may be agony to another.

Winter and Early Spring (January to early April):

For areas that rarely if ever see a frost, including Florida and the immediate Gulf Coast to California, the start of the year is the start of the allergy season. As soon as days start to lengthen a bit, grass begins to grow and releases pollen to spread. By February, the grass is flowering in the Deep South and parts of the Carolinas across the Texas and New Mexico valleys and into central California, with tree pollens joining the pollen party as well.

The grass pollen season expands into the Tennessee Valley and Mid-Atlantic by February and March, with trees likely to cause allergic reactions as far north as the Mason-Dixon Line by early April. Before Easter, residents from the Washington coast, southeastward into the Great Basin and then eastward to the Mid-Atlantic can expect to see that familiar yellow powder pollen coating everything.

Late Spring and Early Summer (late April to July):

Tree pollen season starts to wind down across the extreme southern tier by the latter half of April and May, but it is just getting ramped up further north. Tree pollen is the primary allergen across the northern Plains, Great Lakes and New England during the month of May. Grasses are typically just starting to flower during this time in the northern tier, so residents may occasionally be able to catch a break, but by Memorial Day, expect to see pollen flying in the air and have a tissue on hand for those sneezes.

While grass pollen season continues unabated across the northern tier, making allergy sufferers downright miserable, residents of the Southwest can catch a break. The hot summer days can bake grasses, setting them into dormancy, or a survival-type of sleep. Areas of California, Texas and Arizona that see temperatures surge past the century mark on a regular basis can breathe a sigh of relief for a few weeks in July and early August. However, the dormant grasses can allow the wind to kick up dirt and fields, leading to a peak in the dust season.

Late Summer and Fall (August to December):

A fresh allergen, ragweed, is starting to make its way across the U.S. by the middle of summer. According to the Centers for Disease Control, ragweed, which is actually a flowering plant found near river banks, is the leading cause of allergies, with three-fourths of all sufferers allergic to it. This scourge of sneezers starts to pop up during the latter half of July. The Southeast is usually the first to be subjected to the ragweed pollen season, as it thrives in its hot and humid climate. By late August, ragweed rapidly expands its territory north- and westward, and residents throughout the eastern two-thirds of the U.S. will be feeling itchy and watery eyes.

Ragweed season, and along with it the pollen season, comes to an end as the fall frosts arrive. As nighttime temperatures drop into the 20s, the ragweed plant is unable to survive the chilly conditions. This occurs from north to south, slowly but surely, from September to November. The cooler days, however, lead to a second season of grasses, which are able to wake from their dormancy, spreading their pollen across the Southwest and along the Gulf Coast during October and early November.

The shorter days limit the length of this grass season and they enter another short dormancy before Thanksgiving. Christmas season provides nearly the entire U.S. with another blessing: there are very few outdoor allergens in the environment. However, as soon as the calendar flips to a new year, the cycle starts all over again.

When Are The Worst Times For Allergies?