Compared to the wet April we just finished, May has started very dry this year. How does it rank compared to other years? You can use the SERCC’s Perspectives tool to help answer that question (even if you don’t live in the Southeast).
The map below shows the regional map perspective on the ranking for the month to date precipitation starting on May 1 through May 10. You can see that for many of the stations in the Southeast, except for Florida, the ranking is 1. Most of the stations have a * indicating that it is tied with other years. Note that there are two sets of numbers for each station–the bottom one is for the current location only (often an airport station) and the upper one for the “threaded” record, which is a complete timeline of climate records made by combining or threading two station records together, such as a city and airport record. This would be done to increase the length of record for the purposes of looking at the record highs and lows for each date, but is not appropriate for climatological studies because often the city and airport climates are quite different from each other, and so you can’t just combine them together to look at temperature trends over time since the switch from a city to an airport station will introduce a “false” climate change just caused by the change in the location of the station.
To get the ranking for an individual location, you can either click on the Perspectives map at the station you are interested in or use the “Station Perspectives” tab to pick an individual station. For example, let’s look at Athens, GA at http://www.sercc.com/perspectives?user=true. You can pick your own period of interest or use one of the ones listed below. For now, we will just use the Month to Date. If you click on “View History” it will open and display all the years of record . You can click on the arrows on top of the appropriate column (in our example, let’s use precipitation) to display the values from lowest to highest or reverse. For Athens, it lists a total of three years with zero precipitation for May to date, including 2015, 2014, and 1955. In parentheses behind the value it lists a ranking as T-69 which means it is tied for 69th wettest. [I should note that when I wrote this, May 11 was not over yet, so technically they could get rain before midnight, in which case it should not be included on the list.]
This record is just for the Athens airport station, which has 71 years of record. To get the threaded record, choose your city and then click “Find” to get all the stations in the vicinity. Look for the record that ends in “thr” which indicates “threaded”. For Athens, this is listed as AHNthr or Athens Area. Then click on Update Climate Perspectives to see the complete list. Now you will see that 1913 also had zero precipitation for the month to date and that the ranking is T-108 out of 159 years. You might wonder why there are only 108 rankings if there are 159 years of data–this is because many of the early years from 1857 (when the earliest record started) through 1895 were missing and so could not be included in the ranking.
This tool is particularly useful when you get a call from a local reporter or climate data user asking about how wet or dry, hot or cold it has been.