RALEIGH, N.C. (WNCN) — If you think there's been a lot of pollen in North Carolina this past week, you are right. Central North Carolina hit the highest numbers ever for grass pollen in March, according to the North Carolina Division of Air Quality. The agency operates a pollen sampler in Ra leigh and takes readings every workday. The yellow pollen that seems to be everywhere this week typically comes from trees — and that has hit officially high levels also. Grasses can be more connected to allergies and allergic reactions. Grass pollen allergy is one of the most common causes of hay fever, according to the Asthma and Allergy Foundation of America. These Triad cities will have an especially rough allergy season Grass pollen tends to start in March, but the numbers so far this March at 21 grains per cubic meter of air — are the highest since readings began in 1999, the NC DAQ reports. Tree pollen typically is worse for allergies from smaller trees, such as Juniper/Cedar/Cypress, Elm, and Maple. Those hit very high levels in the first couple of weeks in March. Now, as the yellow pollen is abundant, those readings come from other trees such as Pine and Oak. Tree pollen overall has been at a high level for 15 straight days, according to the North Carolina Division of Air Quality. Grass and tree pollen tend to get even worse in April, but the kind of pollen from trees might not trigger allergies as badly. In fact, the yellow pollen so ubiquitous is actually is usually too large to creep into the sinuses, causing allergy problems. The N.C. Division of Air Quality issues pollen readings on X, formerly Twitter. Click here for the latest pollen readings, which include links to historic graphs and charts for trees, grasses and weeds. ...read more read less