Most larger U.S. cities have one “official” National Weather Service (NWS) weather station for which climate data is recorded and archived. As we weather geeks know, that one location can be very unrepresentative of weather conditions compared with other parts of a city, especially as related to precipitation. Elevation and varying urbanization can provide great differences in temperatures while thunderstorms can drop prodigious amounts of rain in one part of a city, while other areas stay dry. This got me thinking that I had never seen data for either Baltimore or Washington (cities where I grew up), in a format that provided a broader view of these cities’ data. To that end, I decided to undertake the research required using the available climate data of both cities to find out, historically and currently, what other “official” stations (mainly NWS Cooperative Observer Network locations) are available to provide a more comprehensive view of the precipitation records of both locations.

Officially, the National Weather Service (previously known by numerous names and under various Federal Government departments, including the Dept. of Agriculture) began recording official data around 1870. There is available data for various locations prior to this time but the many standards set by NWS might not have been followed, therefore cannot be considered as reliable/official.

Since the late 1800s, both Baltimore and Washington have had nearly a dozen other official stations within their political boundaries recording data for various time periods, some short-term, some longer-term. Additionally, in many instances, the official downtown locations have been discontinued and the new official locations have been moved to nearby airports that could be outside of the city borders. Much of this historical data is now available digitally in website databases (NWS, NCEI/NCDC, ACIS) but much of the older information is not, requiring me to review old paper versions or scanned versions containing handwritten entries. This was very tedious work at times but, being a data wonk, I was determined to provide the best information possible for both cities. Therefore, I began researching state and city publications, dating back to 1870 to find the extremes. This required even reading every page, month-by-month (and annual publications) to make sure I was finding the most accurate, complete data, even the errata that was published in one issue, then corrected in a subsequent issue. This brought up another problem, the fact that the digital databases often contained errors, requiring even more research to figure out what data was correct and where it went wrong. The current results for both Baltimore and Washington can be found in the links below, containing precipitation records for daily/24-hour, monthly, and annual amounts. I’ve also provided the names of all of the stations for which data was reviewed, along with their periods of record.

Baltimore City Limits: Record Precipitation – Daily, Monthly, Annual Amounts

Washington, DC City Limits: Precipitation Extremes

I’ve also been researching temperatures for both cities and will publish that information at a later date.

Take care,

Jeff

Map image courtesy of Bing Maps.