Using the Edition

For information about a manuscript or to see the transcription, go to the Documents section and click on the manuscript. If the manuscript has multiple pages, click on the desired page.

The first observation of a day is designated Reading Number 1, the next observation of that day as Reading Number 2, and so on.

In the transcription view of a page of the daily observation records, click on View Data to see the data fields for the entry. Use your browser’s back button to return to the transcription.

To frame a search of the data in Jefferson’s daily observation records, go to Search.

In the Search section:

To sort search results, use the linked column headings (Date, Time, Location, Temperature, Season, and Natural & Seasonal).

Locations in North America have been designated by NEON (National Ecological Observatory Network) ecological domain.

Seasons are designated by the meteorological rather than the astronomical definition:

Spring: March–May
Summer: June–August
Fall: September–November
Winter: December–February

To download the dataset, use the CSV button at the foot of the Search section.

To explore special features, begin with the Explore section.

For historical background of these records, see the Weather, Climate, & Observation section.

Key to Jefferson’s Abbreviations

Jefferson employed abbreviations to note general weather conditions in the columns of his observation records. He explained his system in a note in the margin of his weather diary for 1784 (see Explanation of Terms, February 1784) and in a letter to his son-in-law Thomas Mann Randolph, Jr., on 18 April 1790.

The core abbreviations were:

c = cloudy

f = fair

r = rain

s = snow

h = hail

a = after

As he explained to Randolph: “Thus c a r h s means, cloudy after rain, hail and snow. Whenever it has rained, hailed or snowed between two observations I note it thus, f a r (i.e. fair after rain) c a s (cloudy after snow &c.) otherwise the falling weather would escape notation.”

He also stated that “I distinguish weather into fair or cloudy, according as the sky is more or less than half covered with clouds.”

He used additional abbreviations in addition to the core terms, such as t for thunder, l for lightning, and d for dew. In the 1784 explanatory key he included b for “bulb,” an abbreviation he used in the temperature column that winter whenever the temperature was so cold that the mercury of his thermometer was down in the instrument’s bulb, “i.e. below 22.”

Some conditions, for example frost, he tended to write out rather than abbreviate, probably to avoid confusion.