We’ve all caught ourselves saying it. “It rains so much more in Carlisle than where I live!” “It always rains on weekends here!” But does it, actually, rain as much in Carlisle as we think?
By: Laura Frangipane
Many blame the zip code and location of Carlisle as being somehow arranged to receive more rain. The idea that the rain could “just” hit the Carlisle zip code without its neighboring towns is false. Carlisle itself is not located in such a way that it receives drastically more rain than other towns in the area. Mechanicsburg, Harrisburg, and Camp Hill were chosen to examine the “uniqueness” of Carlisle’s location in reference to rain. As one would assume logically, Carlisle receives as much rain as these other cities.
One theory for why it may rain more here blames the fact that Carlisle is located in the Cumberland Valley, a valley part of the greater Appalachian Valley spanning the ridge of small Appalachian mountains running from upstate New York and Vermont to Alabama. The Cumberland Valley itself lies within central Pennsylvania and Maryland. The theory goes that it rains more in valleys than in flatter areas of the country, or on mountains.
However, the valley theory is also false. It actually rains more in the mountains or hills bordering a valley than within a valley itself. As clouds are forced to rise above the mountains, their density increases, making the clouds heavier and more liquid, creating more rain.
A second theory is that perhaps it rains more in Carlisle as compared to Dickinsonians’ hometowns. According to the Admissions website, Dickinson students are largely concentrated in the Northeast; 78% of students are from this area, which is defined as running from Maine through Virginia. Of this group, 19% of students are from within Pennsylvania, largely from the greater Philadelphia area. Students from the Northeast are concentrated around its major cities: Washington DC, Baltimore, New York City, Boston, and Hartford (chosen for its central location within Connecticut, where a large portion of students are from). These cities were chosen for this survey and information obtained from the Weather Channel about historical rainfall patterns.
With the exception of DC, every single metropolitan area named above receives more rain per year on average than Carlisle. DC is the lone exception, receiving about 1.5 fewer inches of rain per year (about two days less of heavy rain).
In September, the month the Weather Channel reports as being Carlisle’s wettest month on average, Carlisle had 10 days of precipitation recorded this year. Compared to the other locations used in this survey, Carlisle received an equal amount of days of precipitation. In October of this year, Carlisle received 10 days of precipitation. Of the other locations, some reported up to 12 days of rain.
Some may be wondering if Carlisle then receives more rain in these fewer days, thus receiving heavier rainfall than other areas. However, based on both months’ data, Carlisle receives a lesser amount of rain compared to the other cities reviewed. Carlisle received 6.89 inches of rain in September, while Baltimore received 8.14 inches of rain during the same time period. In October, Carlisle received 2.69 inches of rain, while in Boston 3.9 inches of rain fell.
Historically, the average amount of rain Carlisle receives in September and October is also lower than in the surveyed cities. Carlisle receives 4.28 inches of rain on average in Setptember and 3.22 inches of rain on average in October. New York City receives the most amount of rain in these months, receiving 4.86 inches in September and 4.09 inches in October.
For fun, Carlisle was compared to cities famous for their rainfall, London and Seattle. Surprisingly, Carlisle and all of its Dickinsonian peers received a greater amount of rainfall per year than these towns. Carlisle’s own 41.82 inches of annual rainfall seem huge compared to Seattle’s 38.25 inches and London’s 22.85 inches of rain. What it comes down to then, was the number of days with precipitation that leads to people’s perception that it rains all the time in certain locations. In Seattle and London it rained about half the days of the month, a range from 11-22 days out of September and October. Here in Carlisle and the rest of the Northeast, it only rains about a third of the days of the month, but the rain received is heavier.
Carlisle Drizzle myth… BUSTED.