Forty-five-day temperature differences from normal reveals well-above-average air temperatures across much the Gulf of Mexico and adjacent land masses. (WeatherBell)

From South Texas to South Florida, all along the Gulf and Atlantic coasts, temperatures in the spring frequently have leaped ahead to summer-like levels. South Florida, in particular, has turned downright hot, obliterating long-standing records.

On Monday, Miami experienced its hottest April day recorded, soaring to 97 degrees.

Meteorologists say the steamy weather is linked to abnormally warm temperatures in the adjacent waters of the Gulf of Mexico and Atlantic Ocean and a persistent high pressure zone heating the air.

But both the extent and intensity of the warmth is unprecedented in many areas and would likely not be happening without the influence of human-induced climate change.

Miami heat reaches new April heights

Miami’s scorching 97 degrees Monday was not only a record for the day and the month, but also was the earliest in the year Miami has been that hot — by over five weeks. The day’s average temperature tied as the fourth-warmest day recorded in the city’s history — coming some three months before the typical onset of such summer-like warmth.

Miami already has reached at least 94 degrees four times in 2020, including Monday and Tuesday, which is unprecedented so early in the year.

Miami’s warmth in April, about 7 degrees above average, would classify as the second-hottest May on record, tweeted National Hurricane Center meteorologist Eric Blake.

All of Florida is toasty

The heat hasn’t been restricted to Miami. Virtually every coastal city in the Florida Panhandle and peninsula has seen its warmest or second-warmest start to the year on record.

Year-to-date temperature rankings across Florida. (Southeast Regional Climate Center)

In addition, the National Centers for Environmental Information noted that the past month was the state’s warmest March on the books.

A look at March temperature rankings shows Florida experienced its warmest March on record, while much of the East, South and Southeast saw a top 5 warmest March. Note values correspond to placement in a 126-year history. (NCDC)

Spurts of record heat all along the Gulf Coast

The hot weather has swelled west of Florida all along the Gulf Coast. According to rankings from the Southeast Regional Climate Center, most Gulf Coast areas have seen one of their top five warmest years. Brownsville, Tex., is having its second-warmest year, Houston has warmed into the top three, while the heat has been unprecedented in New Orleans.

Just this week Corpus Christi, Tex., soared to a record high of 96 on Monday, smashing the previous record for April 20 by seven degrees. Nearby Victoria hit a record high of 94.

Houston reached a record of 92 degrees on Easter Sunday.

Farther east, New Orleans hit 90 degrees on April 9 — five weeks ahead of average and the earliest on record the city has been that warm.

Before that, “it was the warmest March on record in New Orleans,” said Phil Grigsby, a meteorologist at the National Weather Service in Slidell, La.

“On March 30, one of my co-workers remarked that a record-high temperature had been set at New Orleans International Airport for seven consecutive days,” he added. That’s the second-longest streak of its kind, narrowly beat out by a string of eight record highs in 2019 and tying with a week of record highs in 2016.

Explaining the heat

Abnormally warm water temperatures and persistent high pressure near Florida and the Gulf Coast have teamed up to bake the region.

Gulf of Mexico water temperatures are hovering some 2 to 3 degrees above normal and, in March, the average temperature was the warmest on record.

Gulf of Mexico sea surface temperature difference from normal. (NOAA)

At Virginia Key, just south of Miami, the water temperature was as high as 87 degrees on Tuesday, more typical of July. The average water temperature at this time of year is around 78 degrees, and records on NOAA’s website show no past April reading even close to Tuesday’s level.

In addition to heating the surrounding air, the warmer waters have added moisture into the atmosphere, playing a role in elevating overnight low temperatures. Since the start of the year, Houston has had nine record-high minimum temperatures.

Gulf of Mexico sea surface temperature anomalies, in degrees Celsius. (WeatherBell)

At the same time, a stubborn dome of high pressure has been shunting any rainmaking weather systems to the north, leaving much of the Gulf Coast abnormally dry. New Orleans and Houston had their fourth- and fifth-driest March on record.

The sinking air associated with the high-pressure dome has discouraged cloud cover, contributing to hotter daytime temperatures.

High pressure (pink) remained stalled between much of February and April, yielding the northward jaunt in pressure lines. That contributed to anomalous warmth along the Gulf Coast and reduced precipitation. (NOAA)

Steven Ippoliti, a meteorologist at the National Weather Service in Miami, noted that the zone of high pressure that’s been hugging the Gulf Coast has also served as a bumper of sorts to deflect cold fronts, preventing cooler northwesterly breezes from making it into the southern part of Florida, where the heat has been exceptional.

Ocean and air temperatures would unlikely be this warm without also taking into account the effects of climate change. Temperatures in this region have risen substantially in recent decades.

For example, data suggest March temperatures in New Orleans are warming more than a half-degree per decade while six of the top 10 warmest Aprils on record in Miami have occurred since 2000.

Implications for tornado and hurricane season

The presence of abnormally warm Gulf of Mexico waters, heated up in part with the help of sunny high pressure parked above, isn’t just reflected in the temperatures across the Gulf Coast. The warm waters also may be contributing to bolstering exceptional rainfall along the Interstate 20 corridor in Mississippi, Alabama and Georgia, and intensifying repeated bouts of severe thunderstorms and tornadoes across the South.

The warmer and extra-juicy air mass isn’t responsible for increasing the frequency of the large-scale triggering storm systems that barrel through, but instead supplies more fuel when they pass by.

There has been some concern about how these toasty waters might influence the hurricane season, which is predicted to be more active than normal. While warm springtime waters in the Gulf of Mexico have no bearing on whether storms form in the Gulf, they could help supercharge any that do if other ingredients are in place.