The first six months of 2020 were one of the wettest starts to any year in Chattanooga with rainfall so far this year nearly 59% above normal.
A record 42.98 inches of rain drenched Chattanooga in the first half of 2020, or nearly 16 inches more than usual, according to rainfall totals recorded by the National Weather Service at Lovell Field. The only year with more rainfall in Chattanooga was 1929, when 45.44 inches of rain fell in the first six months of the year.
The six-month total is only 9 inches of rain less than the total rainfall Chattanooga usually gets in an entire year.
Wettest years in Chattanooga
In the first six month of the calendar year, the most rainfall was recorded in Chattanooga in:
1. 1929 - 45.44 inches
2. 2020 - 42.98 inches
3. 1884 - 42.18 inches
4. 1964 - 41.19 inches
5. 1994 - 41.12 inches
Source: National Weather Service rainfall recorded in Chattanooga January through June. Average rainfall for the period is 27.03 inches and last year there was 39.03 inches of rain in the first half of the year, the 9th highest year on record.
Across the Tennessee Valley, 41.39 inches of rain fell during the first half of the year in the 7-state region served by the Tennessee Valley Authority. That was more rainfall for the TVA region than any year in the 131 years such records have been kept, surpassing even the record rainfalls recorded in Chattanooga in 1929, according to TVA officials.
But as Chattanoogans celebrate July 4th, the National Weather Service predicts the holiday weekend should be much drier with only brief afternoon thunderstorms predicted across the region but no heavy rains in the forecast.
"There's slight chances of rain in the southern Tennessee Valley including Chattanooga, but for the most part it should be hot and relatively dry for the next several days," said Allan Diegan, a meteorologist at the National Weather Service office in Morristown.
Diegan said the Climate Prediction Center is predicting more above-average rainfall this summer in the Southeast as El Niño continues to activate a more active jet stream and wetter-than-normal weather across much of the South, including Chattanooga.
Across the Tennessee Valley, rainfall has been above normal for each of the past nine months, which TVA spokesman Travis Brickey said is a record streak for above-average precipitation in the region.
"If we just get normal rain for the rest of the year, this will still be the third wettest year on record and the third consecutive year of above average rainfall in the valley," Brickey said.
Wettest years in the Tennessee Valley
p>In the first six months of the year, the most rainfall in TVA’s 7-state region came in 2020. Here are the wettest years in the 131 years of rainfall records for the Tennessee Valley.
1. 2020 - 41.39 inches
2. 2019 - 37.79 inches
3. 1973 - 37.42 inches
4. 1994 - 36.71 inches
5. 1974 - 36.35 inches
Source: Tennessee Valley Authority
Heavy rains, especially during February, raised river and lake levels, flooded some low-lying areas and delayed crop planting and some construction projects across much of the Tennessee Valley this year.
But after spilling water at most of TVA's 49 dams through most of the first six months of 2020, lake levels are now normal and the Tennessee Valley is spilling water through only three of its dams — all on the western end of its seven-state region.
Through the wet winter and spring, TVA's network of dams and reservoirs held back 2.2 trillion gallons of water in storage reservoirs upstream of Chattanooga, which is the drainage point in the Tennessee River basin for more than 20,000 square miles of East Tennessee, western Virginia, western North Carolina and North Georgia.
TVA estimates it averted nearly $1 billion in flood damage, including $772 million in damage in Chattanooga, that would have otherwise been caused by the heavy rains if the agency's dams and water management programs were not in place. Without those dams, TVA engineers estimate the Tennessee River would have risen 15.8 feet above what it reached on Feb. 11, leaving many riverfront, downtown and North Shore properties under water.
Before TVA erected its dams on the Tennessee River and its tributaries upstream of Chattanooga, heavy rains in 1917, 1867 and 1891 left much of Chattanooga under water.
James Everett, senior manager of TVA's River Forecast Center, said the winter and spring months were "an ongoing cycle of holding back water to avert flood damage, releasing a large amount to recover storage and balancing Tennessee River flows through a sustained above-normal rain event."
Contact Dave Flessner at dflessner@timesfree press.com or 423-757-6340.