SR SSD 2001-24

Technical Attachment

Analysis of Temperature Readings from Fort Dallas, Florida

Thomas A. Payne, Jr.
Nova High School, Davie, Florida

[Ed. note: This summer, Tom Payne, a student at Nova High School in Fort Lauderdale, worked as a volunteer at WFO Miami. While at the office he studied historical records and did an excellent job of uncovering 19 apparent new record temperatures for the Miami area. He also documented his work with the following paper.]


The National Weather Service provides daily climatological data for the public, 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, Florida, has been recorded at the Miami International Airport. A long-term record from the same site is important so that we may have a history of how things have changed climatologically over the passage of time, and to give us a better understanding of the climate of South Florida. However, to look at an interval of time roughly 60 years in duration (the length of the airport records) and try to assess any kind of longer-term climate patterns is difficult. Observations were taken by the U.S. Weather Bureau at another location from 1911-1942, but those data are regarded by many as questionable due to the location and elevation of the site. 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 skyscrapers, which would make these old readings even more representative of the true natural climate of South Florida because effects of urbanization were non-existent. The purpose of this project was to integrate those observations into data that are recognized by the meteorological community, so that a more accurate picture can be painted of the climate of South Florida.

2. Background and History of Observations

Fort Dallas was one of a series of forts established by the U.S. Government during the three 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 (1835-1842). Temperature records are available, with many breaks, from 1839 to 1855 from the Fort Dallas site (also called "Biscayne Bay") near present day 2nd Avenue SE and 4th Street SE. Records of temperatures and rainfall, also with several breaks, are available from the Fort Dallas site from 1855 to 1858; these observations were taken several times during the day, and were primarily made by the assistant surgeon at the post.

During most of the Civil War, Fort Dallas likely remained in Union hands. (At that time the population of South Florida was sparse and the area lacked any apparent strategic value to either side in the conflict.) The site 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 Florida's 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 (which in fact still exists).

In 1880, the Fort Dallas/Biscayne Bay temperature and rainfall records ended. In 1890, at the request of President Benjamin Harrison, Congress created the U.S. 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 (possibly as a result of two very hard freezes at that time farther north in Florida). Lemon City was a town located near the intersection of present day NE 2nd Avenue and 60th Street (from Larry Wiggins' study entitled "The Birth of Miami," which is available on the Historical Museum of Southern Florida's Web site.)

3. Data and Analysis

Data for this project were obtained from the series of meteorological records described above which detail the temperatures and climate of the forts in the Florida area. These readings were taken during the mid 19th-century and the observations were generally made and recorded by the assistant surgeon at the fort. The data used for this research were extracted from microfilm obtained from the National Climatic Data Center, using a microfilm reader at the NWS Forecast Office in Miami. The film was in average condition, but some of the records were slightly obscured or faded by the passage of time.

The data relating to Fort Dallas were copied from the microfilm onto a spreadsheet program were it could be more easily examined. After all the data were transferred from the microfilm to the spreadsheet, the next step was to examine the daily record high and low temperatures from data taken at the Miami airport from August 1942 to present. This was done to verify whether data obtained from Fort Dallas did indeed eclipse the current records. The records from the Miami airport were obtained from the NWS Forecast Office and a side-by-side comparison was made with the Fort Dallas data to determine whether or not the earlier extremes surpassed the current records.

After careful analysis it was found there were nineteen record highs and lows in the earlier data that were more extreme than the records 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 contained on the microfilm. After the previous results were verified, the confirmed records were compared to the Weather Bureau records in Miami from 1912-1942. These records were largely disregarded for temperature extremes because of the location of the instruments; 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 early data collected by the Weather Bureau was located in the library at the NWS Forecast Office in Miami. After thorough analysis of the Weather Bureau data it was found that the temperature extremes recorded from Fort Dallas were in most cases still greater than any that had been subsequently recorded in the Miami area. Table 1 lists what we consider to be the new record temperatures based on data from Fort Dallas. The accompanying figures are examples from the microfilm records. [Not included here are copies of the microfilm record which document snow and ice in the Miami area, an extremely rare occurrence; and a document showing a temperature which surpasses what is recognized currently as the all-time record low for Miami. The film copies are too poor to reproduce with this tech attachment. Ed.]

4. Conclusions

Current climatological records for Miami are based on observations which date back only to World War II. In order to portray a more 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. The data obtained from this project will allow yet another chapter to be written in the annals of weather history for 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, U.S. 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 Web site, History of the National Weather Service Forecast Office, Russell Pfost, James Lushine, Alvin Samet.

6. Acknowledgment

Special thanks go to Mr. Russell L. Pfost, Meteorologist-in-Charge of the NWS Forecast Office in Miami, for his help and guidance in the writing this paper.

Table 1.

New Record Temperatures from Fort Dallas Observations

Date 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