We recently had to close the Lighthouse to our climbing guests due to moisture in the Tower. This is an interesting phenomenon that occurs, at least in my experience, only in the month of January. January is the month where we experience our coldest temperatures here in Northeast Florida, and this year was no exception. Several nights here on Anastasia Island, the temperature reached to below freezing. During these conditions, the bricks and mortar, granite and marble, that form the Tower, as well as the cast iron landings, stairs and railings, all become very cold to the touch and remain that way on the until the air flowing to the inside of the Tower warms them up again. Then, seemingly suddenly, as temperatures outside increase, a warm air mass with very high humidity surrounds and enters the Tower. As this warm air moves inside the Tower and comes in contact with the very cold surfaces, the water in the air condenses into droplets on all of those cold surfaces. During these times, every surface in the Tower is literally dripping wet, and water can be seen running down the inside walls. We always say, “It’s raining in the Tower”. No amount of wiping or mopping will make any difference until the interior surfaces of brick and iron warm sufficiently to begin to evaporate the water. This usually takes a day or two of significantly warmer air temperatures combined with lower humidity.
A recent foggy night which led to the unprecedented Tower shadow and subsequent morning closures due to “raining in the Tower”.
This same effect can be seen all around our country in the early spring as warmer air moves over the cold ground of the countryside and steamy fog begins to rise off of the frosty fields.
So if you come to visit us in January, you may be able to witness this rare phenomenon in person, but bring your rain gear. It may be raining in the Lighthouse.
Contributed by Director of Museum Services Rick Cain, edited by Student Intern Jayda Barnes