National Weather Service United States Department of Commerce

Analysis of Temperature Readings Taken From Fort Dallas

Thomas A Payne Jr.

Nova High School

Davie, Fl


The National Weather Service provides climatological data for the public daily, including parameters like maximum and minimum temperature, 24-hour precipitation, average and peak wind speed and direction, barometric pressure, and relative humidity. Starting in 1942, climatological data for Miami has been recorded from the Miami International Airport. This is done so that we may have a history of how things have changed climatologically over the passage of time and give us a better understanding of the climate of South Florida. However, to look an interval of time roughly 60 years in duration and assess any kind of long-term climate patterns from such a limited amount of data is difficult. Even if one were to include the observations taken by the Weather Bureau 1911-1942, which is regarded by many as questionable due to the location and elevation at which the observations were taken. Thus, the amount of data that is available for Miami climatological analysis is marginal, and this project seeks to further our knowledge in this area.

During the mid 19th century, temperature observations were taken by the assistant surgeon stationed at Fort Dallas, an outpost built during the Seminole Wars. These records were taken when South Florida's landscape was dominated by the Everglades instead of by skyscrapers, which would make these readings even more representative of the true natural climate of South Florida because effects caused by urbanization were non-existent. The purpose of this project was to integrate these observations into data that is recognized by the meteorological community, so that a more accurate picture can be painted of the climate of South Florida.

2. Background Information.

Fort Dallas was one of a series of forts established by the U.S. Government during the Seminole Wars from 1816-1818, 1835-1842, and 1855-1858. The first weather observations made in what is now the Miami area were taken at Fort Dallas during the Second Seminole War. Temperature records, with many breaks, are available from 1839 to 1855 from the Fort Dallas site (also called "Biscayne Bay") near present day 2nd Avenue SE and 4th Street SE. Temperatures and rainfall are available from the Fort Dallas site from 1855 to 1858 with several breaks; these observations were taken several times during the day, and were primarily made by the assistant surgeon.

During the civil war, Fort Dallas likely remained in Union hands. This was due primarily to South Florida's sparse population and apparent lack of strategic value to the confederates during this time. However, it was likely used as a base for ships participating in the naval blockade of the Confederacy. In 1870, President Ulysses S. Grant signed a joint resolution of Congress establishing a weather service within the Army. Observations were taken at 22 sites by the Army Signal Corps and the word 'forecast' was first used. An Army Signal Corps weather observation site was established at Punta Rassa (near Fort Myers) on the West Coast, and later at Jupiter in Palm Beach County on the east coast. Meteorological observations taken in the Miami area between 1870 and 1880 were called 'Biscayne Bay' and seem to have been taken at least part of the time on Key Biscayne where a lighthouse was located.

In 1880, the Fort Dallas/Biscayne Bay temperature and rainfall records ended. In 1890, at the request of President Benjamin Harrison, Congress created the Weather Bureau within the Department of Agriculture. Unfortunately, no meteorological records were kept in the Miami area again until September 1895, when a new station was established at Lemon City (again possibly as a result of those two freezes farther north in Florida). Lemon City was a town located near the present day intersection of NE 2nd Avenue and 60th Street. From Larry Wiggins' study entitled "The Birth of Miami" available on the Historical Museum of Southern Florida's web site.

3. Data and Analysis

Data for this project was obtained from a series of meteorological records detailing the temperatures and climate of the forts in the Florida area. These reading were taken during the mid 19th century and the observations were generally made and recorded by the assistant surgeon at the fort. The data that was used for this research was taken from microfilm that was obtained from the National Climatic Data Center. The film was examined through a microfilm reader located in the library of the Weather Forecast Office, Miami, FL. The film it self was in average condition, as some of the data contained therein was slightly obscured or faded by the passage of time. The data relating to Fort Dallas was copied from the microfilm on to a spreadsheet program were it could be more easily examined. After all the data was transferred from the microfilm to the spreadsheet, the next step was to examine the daily record high and low temperatures that taken from the Miami airport from August 1942-Present. This was done to verify that the data obtained from Fort Dallas did indeed eclipse the current records. The records taken from the Miami Airport were obtained from the Weather Forecast Office, whereupon they were photo copied. A side-by-side comparison was made to whether or not the observations taken from the fort were extreme enough to surpass the current records.

After careful analysis it was found that there were nineteen record highs and lows that were more extreme than the records that were taken from the Miami Airport. This being done, the next step was to confirm the accuracy of the data on the spreadsheet to the hard copy of the data that was contained on the aforementioned microfilm. After the previous results were verified, the confirmed records were compared to the records taken by the Weather Bureau of Miami from 1912-1942. These records were largely disregarded for temperature extremes because of the location of the instruments that took the results; however, it was necessary to cross check our records against these observations so that an all-encompassing record of climatological data could be formed. The data collected by the Weather Bureau was located in the NOAA library located in the Weather Forecast Office, Miami, FL. After thorough analysis of the Weather Bureau's data it was found that the temperature extremes that were recorded from Fort Dallas were in most cases still greater than any that had been previously recorded in the Miami area. Table 1 lists the new records from Fort Dallas data and the visuals give an example of some of the data taken from the microfilm. Figure 1 is a documentation of frost and ice, which in Miami is a rare occurrence. Figure 2 documents a temperature that surpasses the current record low. Figure 3 is an example of how the data was presented on the microfilm, and the format that it was in. The data obtained from this project will allow yet another chapter to be written in the annals of weather history of Miami.

Figure 1.

Figure 2.

Figure 3.

Table 1.

New Record Temperatures from Fort Dallas Observations


Old Record

New Record Observation from Fort Dallas

January 3rd

Low-38 1962

Low-37 1841

January 17th

Low-39 1965

Low-30 1841

January 20th

Low-31 1977

Low-30 1857

February 13th

Low-40 1955

Low-36 1841

February 27th

Low-41 1965

Low-40 1855

April 22nd

Low-59 1943

Low-54 1856

April 23rd

Low-57 1986

Low-55 1857

April 24th

Low-60 1986

Low-50 1857

May 20th

Low-64 1951

Low-63 1857

May 30th

Low-67 1945

Low-64 1841

August 16th

Low-72 1959

Low-71 1841

August 21st

Low-71 1957

Low-70 1841

September 17th

Low-72 1989

Low-71 1841

December 3rd

High-85 1991

High-86 1850

December 4th

High-85 1983

High-86 1850

December 16th

High-85 1947

High-86 1850

December 19th

High-85 1989

High-87 1850

December 22nd

High-86 1948

High-87 1850

December 30th

Low-39 1961

Low-36 1839

4. Conclusions

Current climatological records for Miami date only back to World War II. In order to portray an accurate depiction of the climate of the Miami area, it seems logical to include all available temperature data. The first step in this project was to examine data from Fort Dallas, a Seminole War outpost in the mid 19th century. Nineteen new record temperatures were discovered in this process, including two new observations below freezing. This new information will allow yet another chapter to be written in the annals of the climatology of Miami.

5. References

U.S. Dept. of Commerce, National Oceanic and Atmospheric Administration, National Climatic Data Center, Climatological Data (Miami, Florida), years 1942-2001

U.S. Dept. of Commerce, National Weather Bureau, Climatological Data (Miami, Florida), years 1911-1942

U.S. Weather Bureau, National Archives, Climatological Records (Florida) 1819-1892

U.S. Dept. of Commerce, National Oceanic and Atmospheric Administration, National Weather Service Weather Forecast Office website, History of the National Weather Service Forecast office, Russell Pfost, James Lushine, Alvin Samet.

6. Acknowledgements

 Special thanks go to Mr. Russell L. Pfost for his help and guidance in the writing of this paper.