By Linda Lam: Weather.com:

Weather plays an important role in how much pollen is produced, its distribution and how much pollen is in the air at a given time. Allergy symptoms are often reduced on rainy or windless days because pollen doesn’t circulate as much during these conditions. Pollen tends to travel more with warm, dry and windy weather, which can increase your allergy symptoms.

Pollen counts vary by time of day, season and weather conditions. Rain, wind and temperature are all important factors to consider when determining if pollen counts will be high, moderate or low on a particular day.

Overall, pollen counts tend to be higher in the morning, as well as on warm, dry and windy days. Conversely, lower pollen levels are also typically observed during a stretch of cold and wet days. The National Institute of Health Medline Plus recommends saving outside activities for late afternoon or after a heavy rain, when pollen levels are lower.

Pollen is transported in the air and enters our respiratory system, triggering an allergic reaction technically called allergic rhinitis. According to the National Institute of Allergies and Infectious Diseases, a branch of the National Institute of Health, approximately 35 million Americans complain of upper respiratory symptoms related to pollen.

Give and Take Between Rainy and Dry Conditions

Rain can bring relief to allergy sufferers, at least for a while. Humidity and rain prevent pollen from traveling, as moisture weighs down the pollen, keeping it on the ground according to webmd.com.

Rain often washes pollen out of the environment, but first, heavy rain bursts pollen particles, spreading allergens farther, said Dr. Warner Carr, an allergist and fellow of the American College of Allergy, Asthma and Immunology.

“During a rainstorm, the pollen in your environment gets saturated and fractures, releasing small particles into the air at a much higher concentration,” Carr explained. The small particle can also be inhaled deeper causing more difficulty for allergy sufferers.

Rain can also aid in the growth of grass, plants and trees which later increases the production of more pollen. A better scenario would be a daily rain shower over several days, as alternating rain and dry weather may again cause symptoms, according to Dr. Massoud Mahmoudi, a board certified physician in Internal Medicine and Allergy & Immunology.

Another factor is how much rain occurred in the late fall and during the winter. Rainy winters and autumns can increase pollen levels in the following spring, due to an increase in tree pollination amounts says Pollen.com.

Lack of rain can be a good thing for allergy sufferers as growth of trees and plants is typically slower. Dry conditions and drought can reduce allergens since plants wouldn’t be growing as abundantly, according to Jeff Haby at theweatherprediction.com.

Drought makes it harder for pollinating plants to grow. If you are allergic to pollens produced by weeds, trees or grasses, drought may mean less pollen and fewer allergy symptoms, says Chris Illiades, MD. If you are allergic to molds, however, the dry and hot weather may lift spores from the soil into the air, potentially making your allergies worse.

If it is windy at all, however, dry conditions can make it easier for the wind to pick up pollen and carry them to your airway, exacerbating allergy symptoms.

Wind helps pollen travel from the source of the allergen to our respiratory system. Windy conditions stir up dust, mold, pollen and this may activate allergies, according to Weather Underground. The tiny pollen particles can also travel far from its originating point in the wind.

On a dry and windy day, loose pollen is easily scattered in the air, making wind a very important factor in determining the potential for an allergy sufferer to experience symptoms.

A mild winter can mean an early start to the allergy season. Mild temperatures can bring an earlier onset of pollination of trees and plants. If the mild conditions persist into the spring, higher pollen counts will be found earlier in the season.

Changes in temperatures during the spring play an important role on the pollen levels. Warm temperatures will lead to an increase in pollen counts. However, sudden drops in temperature can freeze tree pollen production, according to infoplease.com.

Frequent large temperature variation can also add to a person’s sensitivity to allergens. Dr. Clifford Bassett, founder and medical director at Allergy and Asthma Care of New York, says the priming effect is when temperatures make big leaps in small periods of time.

For instance, when one day the weather is around 30 degrees and the next the mercury rises to 70 degrees, “that’s when people really start to suffer.” The constantly changing and highly varied temperatures cause your body to “[rev] up the immune system and further on down the road, you’re going to be even more hyper-sensitive or hyperactive to the new pollen.”