Weather + Climate

Monthly weather and climate data can be found here for the State of Georgia and the City of Atlanta. All Atlanta data is from National Weather Service instruments located at Hartsfield-Jackson Atlanta International Airport. Data has been collected at that site since 1930. Quick data points and rankings are posted on the right side of the homepage (below posts for mobile users). All data is pulled from the National Oceanic and Atmospheric Administration (NOAA) websites and is updated on a daily and monthly basis. Georgia temperature data and drought data for the previous month is released by NOAA several days into the new month (ex: January data is released around Feb 7th).

Keep in mind that scientists don’t simply look at raw data to assess changes in the climate. Quality control methods must be applied to weather stations to ensure they are not capturing inaccurate or erroneous data. Adjustments of observed temperatures may also occur. As land gets developed, localized temperatures generally warm. This is known as the urban heat island effect. Scientists must adjust for this as well as changes in the quality of instrumentation over time. The significant bulk of adjustments have occurred to data observed prior to 1940 and those adjustments have generally resulted in warmer temperatures. The adjustments made over the past several decades have generally resulted in minimal changes from the observed data. Popular Mechanics has a good article about how scientists determined in 2012 that the old global temperature record of 136.4°F recorded in Libya in 1922 was not credible. Death Valley, California now holds the global record of 134°F, recorded in 1913.

 

Current Conditions

Current Temperature Chart (Blue Line-Red Digits)

This is the top chart that appears to the right (desktop) or below the article (mobile). All data is updated on an hourly basis. The two right-most data points show today’s average temperature and the normal average temperature for today. The average temperature is simply the high for the day plus the low for the day, divided by two. NOAA’s definition of “normal” is based on data collected between 1980 and 2010.

 

Historical Monthly Temperature Chart (Colored Dots)

The chart with the colored dots on the right (desktop) or below (mobile) shows the average month-to-date temperature for all years going back to 1930. The black star represents 2018. The month-to-date average temperature is the average temperature from the first of the month through today. For example, on June 30 there were 8 years with warmer June 1 to June 30 (month-to-date) average temperatures than June 1 to June 30, 2018. That makes June 1 to June 30, 2018 the 9th warmest June 1 to June 30 on record, which is reflected on the bottom chart.

 

 

Average Temperature by Decade

The chart below shows the average month-to-date temperature for each decade.

 

Monthly Rank Chart

The third chart on the right (desktop) or below (mobile) shows how temperatures up to this point in the month compare to historical temperatures up to this point in the month going back to 1930. Since our graphs update on an hourly basis, the ranking may change throughout the day as today’s latest temperatures get incorporated into the historical comparison.

 

Rank Change Throughout the Month

The chart below shows how the ranking has changed throughout the month, so you can track fluctuations. The rankings shown on the chart are recorded at the end of each day.

 

Temperature Needed to be First Warmest or First Coldest

The chart below shows what average temperature is needed today for our month-do-date ranking to be the 1st warmest or 1st coldest. So if it’s the 15th of the month and our month-do-date ranking is 6 then the left-most temperature on the graph represents the average temperature we need today in order for the ranking to move from 6th to 1st. If it’s the 15th of the  month and our ranking is already 1st warmest then the left-most temperature represents the maximum average temperature needed today for our ranking to drop from 1st to 2nd. These temperatures will often be impossible to achieve, but they provide a general indication of how much warmer or colder temperatures have been in previous years compared to this year.

 


State of Georgia Average Temperature

The figure below shows the average temperature up to that point in the year for the State of Georgia versus the historical 20th Century Average for that time period. Average daily temperatures are calculated by adding the high temperature to the low temperature and dividing by two. All the daily average temperatures are then used to determine the monthly average temperature.

NOAA has provided a ranking tool to put the data into historical context. Using 123 years of recorded data, the tool shows you how data for a particular time period compares to historical data for that time period.

The chart below uses the Year-to-Date feature to show how warm or cool the year has been up to that point compared to previous years up to that point. For example, the average temperature in Georgia from January 1, 2017 to February 28, 2017 was 54.8ºF (red bar). Historically, the average temperature during that period is 47.4 °F (black line). This is a departure from the historical average of +7.4 °F. In 123 years of record keeping, January 1, 2017 to February 28, 2017 was the 3rd warmest such time period of any year.

 

October Analysis

A very warm September and warm October has resulted in our year-to-date average temperature being 1.6°F above average. This ranks as the 11th warmest January to October on record.


City of Atlanta Average Temperature

The figure below shows the actual average monthly temperatures at Hartsfield Jackson Atlanta International Airport versus the normal average monthly temperatures. The numbers at the base of each bar represent the difference between the actual average monthly temperature the normal average monthly temperature. For example, in April 2017 the actual average monthly temperature was 67.8 °F and the normal average monthly temperature was 62.0°F. The average temperature was therefore 5.8°F above normal. The Year-to-Date is the average of the actual and normal monthly temperatures from January 1st to the end of the previous month. All data is from the National Weather Service Forecast Office in Peachtree City, GA.


October Analysis

October 2018 was the fourth warmest October on record. The month was marked by a very warm beginning and fairly cool end. We set a record high on the third and tied a record high on the 7th. As warm as those days were, our high on the 26th only managed to get a couple degrees above the normal low for the day. Only five of the last 24 months have seen temperatures below average.


 Atlanta Average Precipitation

The chart below shows the actual monthly precipitation recorded at Atlanta Hartsfield International Airport (blue bar) versus the average monthly precipitation (blue line).  All data is from the National Weather Service Forecast Office in Peachtree City, GA.

October Analysis

We recorded a 1.34 inch surplus of rain in October, which pushed our yearly surplus to 9.33 inches.


Drought Conditions

The Palmer Drought Severity Index (PDSI) is a widely used model designed to predict drought conditions. The PDSI has its advantages and disadvantages, but NOAA and state and local governments use it to assess drought conditions over time. Negative numbers correspond to drier conditions while positive numbers correspond to wetter conditions. A PDSI value of -4.0 or below corresponds to extreme drought conditions.

Each state is divided into climate divisions with Georgia having nine division. They are numbered from northwest to southeast; metro Atlanta is in District 2 (second from top left) as is Lake Lanier, one of the state’s most important reservoirs. Drought conditions both upstream and downstream of Lake Lanier will influence the reservoir’s water levels. Drier conditions in District 2 and 3 will result in less water flowing into Lake Lanier while wetter conditions in south Georgia and Florida can result in less water being released from Lake Lanier. Tensions in the water wars between Georgia, Florida, and Alabama escalate as drier conditions increase in the southeast region. Below is a GIF of PDSI values for every climate division the country.

 

 


 

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