First, lookup the maximum wind speed for your location. Any flagged flagpole not rated for this wind speed will be removed from the results.
Maximum wind speed is generally between 85 - 170 mph. This is also known as the nominal design wind speed as determined by the ASCE 7-22 Standard. Wind speeds correspond to approximately a 7% probability of exceedance in 50 years (annual exceedance probability = 0.00143, MRI = 700 years).
Next, choose the type of flagpole you're looking for.
