Austinites went into this summer bracing for the worst. After two back-to-back summers of record-breaking heat, many expected more of the same. So far, it has been very hot, sometimes dangerously so, but the worst has not come to pass.
For example, the forecast shows highs in the 90s for the next six days. A prospect that has many thinking, “I’ll take it!”
On Thursday, approaching mid-July, it was 70 degrees at the airport. Again, “not bad!”
These slightly less scorching conditions have a lot of Austinites wondering, “How long could this last?”
To answer that question, we need to know why it’s been a little cooler in Texas and hotter elsewhere.
Let's take another look at our friend, the heat dome
If you were in Austin last year, you likely remember the “heat dome.” This is what people called the high-pressure system that spread over Texas and stayed through the summer.
That high pressure was the trigger for the consistently high temperatures last year.
This year, it looked like it might strike again.
"What is that ridge of high pressure gonna do this year?” National Weather Service meteorologist Victor Murphy asked in June. “If it does build northward into Texas like it did last year… I don't want to think about it.”
But so far, a stubborn, constant heat dome has not materialized.
Instead, high pressure has centered over states to our west. And their loss is our gain temperature-wise.
“You may have seen stories about Las Vegas hitting an all-time record high,” NWS meteorologist Nick Hampshire said. “That general area of the United States [is] much hotter than expected. So it’s been a little bit more bearable here.”
The knock-on effect
The absence of that high pressure over Central Texas has allowed for other weather conditions that promote cooler air.
For one thing, weaker high-pressure systems provide a greater chance of rain in Austin even in our typically dry summers.
That’s exactly what we got last Saturday when part of the city received more than an inch of rainfall. The storm brought cooler weather and injected water into the soil.
When the earth is wet, it tends to hold triple digits at bay for longer because the sun’s energy works to evaporate that water rather than bake the ground.
Then you have to consider Hurricane Beryl, Hampshire said.
The storm likely had an even greater impact on recent lower temperatures, even though Austin avoided its rains and heavy winds.
“In the wake of those tropical systems, especially with the cloud cover, it can be a little bit cooler than what would have otherwise happened,” he said.
The hurricane's path was also dictated by where that high-pressure system was sitting over the continent.
“The center of that [high pressure] being to our west kind of caused everything to happen,” Hampshire said. “The slightly cooler temperatures, Beryl working up this way, and some afternoon rain chances are all because that high pressure is not on top of us.”
That could change.
So how long will the cooler temperatures last?
High-pressure systems can stubbornly stick in one place like they did over Texas last year, or they can move around.
It looks like the high-pressure system that's hanging out further west will start moving east by next week.
Hampshire said if it reaches our area, that could easily bring another stretch of triple digits.
In case you’ve forgotten, last year Austin had 45 triple-digit days in a row.
But, even if we avoid that fate, it’s worth remembering that Austin will most certainly be hotter this summer than it has been for most of its history.
Take this example. Back in the '90s Austin averaged about nine triple-digit days in an entire year.
This year, even as it's felt "cooler" than recent summers, we have already hit that mark.
It's a reminder that global warming is not only heating the atmosphere but changing our perceptions of what hot weather really is.
