From the Tulsa World newspaper:
Allergy alerts are expected to continue several more weeks across Oklahoma, as so many species of trees are creating pollen that rain in the forecast is only likely to exacerbate the problem.
Last week, oak and cedar pollen prompted three straight days of allergy alerts. This week's pollen counts include "extremely high" levels of pecan, ash, mulberry, sycamore and oak, said Dr. Greg Metz of the Oklahoma Allergy and Asthma Clinic.