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Details of Ragweed Season

ragweed season

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Last August Through September

Ragweed season begins just as the summer grass allergies are beginning to let up. Weeds such as ragweed and giant ragweed account for the majority of cases of hay fever in the fall months.

This occurs from late-July/early August through the end of October, with the peak of the season occurring during August or September depending on the region. For people in the southern states, the peak pollen production occurs during mid-September.

The season comes to an end with the onset of cooler weather in the fall months and therefore ends earlier the farther north you go. Unfortunately however, with steady increase in temperatures across the US over the last two decades, the season has begun lasting long and longer.

Ragweed is Lasting Longer

Because ragweed thrives in hot weather, if these conditions last throughout the summer, the amount of ragweed pollen produced will be very high. It was found that the season lasted a full 27 days longer in 2009 than it did in 1995.

Even in areas where the season did not last longer, pollen production as a whole was up dramatically. This has contributed to the endless growth in allergy and hay fever sufferers across the US.

Factors Effecting Each Season

Aside from cooler temperatures, which result in a milder season, the main factor influencing the length and intensity of the season is the amount of rainfall.

In areas with record low rainfalls during the summer, the season will be relatively short during the fall. Abundant rainfall during the summer months however will result in significant pollen production during the fall flowering season.