In brief: The Gulf tropical disturbance is unlikely to develop, but it will bring some rain to the area tomorrow and Saturday. We have one more shot at 100 today before a brief break. More 100 chances return next week. Today we also dive into Bush Airport and talk about why it seemed to be such an outlier on Tuesday.
First, the tropics
Let’s start quickly this morning with the tropics and on this disturbance we have moving across the Gulf today and into our region tomorrow. There continues to be little to no chance of development with this. For Greater Houston, that means an increase in rain chances tomorrow and Saturday. And even that should be manageable.
Now, how much rain? Well, Friday will be interesting. It could go one of two ways I think. The first way? The disturbance approaches Texas and we get a solid rain shield offshore, so coastal areas see a fair bit of rain in the morning, with inland areas seeing just a few scattered afternoon thunderstorms. Alternatively, we see a small bit of rain in the morning at the coast and then more numerous showers and afternoon thunderstorms moving southeast to northwest across the region. I am leaning heavily toward the coastal rain outcome, where inland areas see some scattered storms but nothing too widespread. This means folks in Galveston could easily see a couple inches of rain, and more numerous showers and storms may push across Brazoria, Galveston, and Chambers Counties.
On Saturday, we’ll probably see a repeat, except I think storms could be more numerous across the entire region. As we’ve been saying, it should not be a total washout, but you’ll want to have some rain plans in place on both Friday and Saturday if you’re planning outdoor activities.
Rain totals will be on the order of probably 1 to 2 inches at the coast and a gradual trailing off of rain inland down to about a half-inch to inch inside the 610 Loop and less than that farther inland on average. Some areas may see little to no rain. Other isolated pockets, especially south and east of Houston could see 3 to 4 inches of rain.
Next, the heat
We hit 99 degrees yesterday, and we will make another run for 99 or 100 today probably. With clouds and showers around, Friday and Saturday should be substantially less hot. But look for the heat to return Sunday or Monday, and we will be making another run at 100 degrees by Tuesday or Wednesday.
Is the IAH thermometer rigged?
The fun thing about weather is that no matter where you live, if something looks the slightest bit suspicious, people start weighing in with lukewarm and hot takes about why there’s something wrong with a temperature sensor, someone has an agenda and is purposefully fudging data, and on and on. One of my favorites is when Washington, DC gets snow, virtually the entire city gets mad at whoever measures the snow at Reagan Airport because it is obviously too low. In Philadelphia, you get the opposite, the snow totals almost always get yelled at by people for being inflated.
Well, we’ve got ourselves a fun game of this happening in Houston now. On Tuesday, when IAH hit 100 degrees, many people were convinced it made no sense.
And, honestly, looking at that map above, I get it. IAH does stand out. Out of an abundance of caution, the NWS sent their electronics technician out to look at the thermometer at IAH. It was fine. It was reading where it should have been, and there have not been any recent changes near the thermometer. Turns out, it’s just hot at IAH. If you look at the high temperatures on Tuesday from a number of additional weather stations, filtered for most of the clearly bogus values (50s, 110s), you’ll see multiple spots hit 100 degrees.
I’m not going to say that each of these weather sensors is sited perfectly or calibrated perfectly, but based on what I saw from sensors that I trust on Tuesday, I would have expected IAH to top off around 98-99 degrees. So, 100 doesn’t exactly shock me. But it’s definitely at the top end of temps for our area.
So, what is the deal with IAH, and can we trust it as a long-term indicator of our climate? It’s a complex and complicated question to answer. In most cities, historical data did move from essentially the center of town “back in the day” to airports. Official readings are now almost always taken at airports, where no one actually lives, of course.
A few places are unique or have complexities: Think Central Park in New York City; not an airport and a good, long historical data record. In Austin, you get to choose from Bergstrom Airport or Camp Mabry, two locations that can be very, very different during certain events. Downtown Los Angeles has also had a checkered history, with a weather station that has now moved 8 times. The linked article is from 2014, when USC housed the official Downtown L.A. sensor. It now sits on the south side of Dodger Stadium. The next time I visit SoCal, I intend to wear an Altuve jersey, go stand by it, and boo it. When stations like this move, there’s a process called “threading” that occurs. This process is by no means perfect, but it does a fairly good job of ensuring that station discontinuities are accounted for and the extremes we’re measuring against historically are as unified and realistic as possible.
Is IAH a reliable indicator of Houston’s weather history? Ten people will have ten opinions on this, but the reality is that it’s not really any worse than any other spot in the area. Houston is constantly evolving, growing, and changing. IAH isn’t perfect, but I think the important takeaway would be that there’s a difference between being representative of where people live versus being representative of reality at a given point. IAH isn’t a reliable indicator of every neighborhood’s weather history in Houston. But it is reliable as a location for our climatology today. In other words, compare IAH to IAH, not IAH to elsewhere. IAH hit 100 on Tuesday. Compared to previous records at IAH, it was one degree shy of a record high. That doesn’t mean that Sunnyside was 1 degree shy of a record. Or Sheldon was 1 degree shy of a record. IAH was. And since our official records are kept there, “Houston” was. You could make a similar argument about DFW Airport, which keeps Dallas’s official records or O’Hare in Chicago or Logan Airport in Boston.
Going back to the 100 on Tuesday, one of the key reasons for it may have been the lower humidity we saw that bubbled up in a pocket of the city. We can assess that with dewpoint values, as seen below. Also, IAH had 42% relative humidity at 3 PM, right around when it hit 100 degrees, which was one of the lowest relative humidity values in the city at that time.
Drier air heats up more efficiently than more humid air, and when you have an air mass this hot, it doesn’t take a massive change in humidity to lead to a somewhat outsized change in temperature. Bottom line? It seems that a localized pocket of low humidity impacted the area near the airport. When combined with the already generally hot location of IAH, it led to a bump to 100 degrees on Tuesday, when most other locations were more like 96 to 98 degrees.
Does this settle the debate? Never. Everyone will still have opinions on this. Weather is a bit like sports in that regard, I guess. But when thinking of IAH, it’s a microcosm of all the things influencing our history here: Urban heat island, sprawl, a warming Gulf, and climate change all playing roles. But we wanted to share some of the plausible reasons why it happened, as well as add some color on IAH. Not perfect, but it’s what we’ve got.
I guess the idea of moving so many official reporting locations to airports has to do with the improbability of the airport being demolished any time in the foreseeable future. But surely, an area that is always going to have large expanses of concrete paving and zero tree cover is going to be a few degrees hotter than most other areas in the city?
…large expanses of [] paving and zero tree cover…
This description applies to a significant part of the city including a majority of the suburbs.
Eh. Most of the ‘burbs (and even downtown) have at least a smattering of trees. There aren’t a ton of areas so wide-spread yet utterly denuded of anything taller than grass than the IAH complex.
Matt, that you were able to make a multi-paragraph discussion about temperature sensors such an interesting and enjoyable read is a testament to your skills as science communicator.
Yeah! ☺️
It’s interesting to use weather satellite websites that show GOES longwave-IR images. When it clear and cloud-free you can watch broad area temperature differences. Overnight you can often see the area pretty much bounded by the Grand Parkway around Houston remain warmer than the more open areas around it across southeast Texas. It’s an obvious indicator that IAH and other large metropolitan area official temperature reporting stations are biased towards higher temperatures.
IAH temps are affected by inputs like jet engine exhaust and enough HVAC equipment to cool several million square feet of terminals, hotels and out buildings. My neighborhood temps in SE Houston are routinely 5 degrees cooler. To avoid most of the urban heat island effect, thermometers should be in a greenfield.
Why should thermometers be located to avoid the effects of urban heating? I live in an urban environment. I live around concrete, asphalt, roofs, HVAC, and cars. The sensor is being used to report current weather and predict future weather. Don’t you want the sensors to accurately reflect the area they are being used for prediction? If you want to know YOUR current air temperature where you are located then shouldn’t you locate the sensor where YOU are?
The whole point of today’s post was to show that sensors are located where they are located for a lot of reasons. If I read IAH’s sensor and say “well jeez its not 100 deg F where I live 30 miles away”, then that is an obvious statement.
70 degrees dewpoint? Not too bad!
Love the “wear an Altuve jersey and boo outside Dodger Stadium.” After the Astros swept them in LA a couple weekends ago, I went to their Instagram page, stated I was an Astros fan, and advised them that Altuve had his AI drone in the air over the weekend and it was stealing the Dodgers’ pitch signs. Then it instantaneously relayed this to Bluetooth devices in the Astros’ batters ears. It’s fun to mock their odious fans, who are in the same class as Yankee fans.
….okay??? You all right?
Sir this is a Wendy’s
We have a Tempest weather station at our house. It read 100.4 for Tuesday, then 102.6 yesterday. We are in NE Harris County, so not that far from IAH as the crow flies.
We have a thermometer outside and that is the temperature we go by. We live 5 miles north of houston city hall.
As another off the wall comment, could the higher temperatures at IAH be caused or affected in any way by the large number of mobile kerosene heaters running around on the runways, taxiways, etc?
Good discussion.
Joe
So basically, instead of it being hot af, it’s hot iah 🙂
Clearly IAH temps are influenced by an amplified heat island effect because there’s so much concrete. /s
We have an Ambient Weather Station that I posted on a 10’ pole in our backyard. It’s given us some pretty reliable temps over the years and that includes yesterday when it hit 100.8. It was HOT. We live in NW Houston splitting the Cypress/Tomball zone.
Come for smart insights about the weather. Stay for the Dodgers slander. I love SCW!
Last I looked, IAH has a lot of concrete around it.
I love all the comments trying to write off IAH’s temperature readings while totally ignoring the nuance of Matt’s explanation and also ignoring the point about the trends being important.
“Compare IAH to IAH, not IAH to elsewhere.”
When IAH became the official site for Houston in 1969 the airport had two terminals and two runways and it was built in the middle of nowhere. Now look at the at the difference.
NWS has extensive requirements for temperature measuring, including that the thermometer be over earth/sod, and 100’ from concrete. Buffer zones around runways are good for this. Airports have secured areas, and weather data at the landing site is pretty useful for aviation. Lots of reasons that airports are attractive for weather stations.
Today’s update discusses variation in rainfall and temperature over the Houston area. I would be interested in a deep dive into how forecasts are localized. Conroe vs downtown vs Galveston spans more distance and climate features than some states. How do the weather apps slice and dice the “Greater Houston Area” to show temperature and rainfall predictions for the inner loop vs Clear Lake for example? And if differences are predicted, are the differences based on directly computing the data, based on point samples of regional weather models, or based on some sort of hand-waving interpolation between points with rigorous forecasts (i.e. Houston will be 100 degrees, Galveston will be 90. Clear Lake is in the middle, so temp will be 95).
I would like to think a professional meteorologist gnome is sitting in my phone, crunching all of the numbers, consulting the supercomputer models, and typing out forecasts for my block à la minute. We probably don’t have that, but Eric & Matt do pretty good.
Comparing IAH to IAH is not perfect either. All temperature/ rainfall records were moved to IAH in 1969. So any current standing record before that time was measured in downtown Houston.
Believe it or not we had a rare July cool front in 2019 which dropped it into the 60s across the region on this day hence the record low of 68 at Bush Airport for today.
This is why I addressed the “threading” of climate data. It’s meant to reduce that impact.
People get worked up about very little these days with constant data flow, and if it wasn’t for 24 hour social media crap it would matter little whether the temperature is shown to be 98 or 102 or anything between, it’s still horribly hot.
The local media was all pushing this
“ it’s the first 100 degree day in Houston”
July 24th
Record high: 101 in 1954
Record low: 68 on 2019
Strange reactions as if 100 is so much hotter than 99…
Kind of like the hysteria when a cluster of tropical storms get a closed circulation and sustained 35 mph winds and earns a name… or even more so when that same cluster of storms graduates, gets sustained winds of 75 mph and becomes a hurricane.
I guess we have to draw lines somewhere and for some reason reaching 100 is somehow next level heat…
Congrats on answering your own question. The line has to be drawn somewhere. If it was at 90, you’d be in here like “strange reactions as if 90 is so much hotter than 89….”
Guarantee it.
Exactly and what’s funny about that is the fact that often times when air temperatures reach 100 degrees here the humidity levels drop a bit so the heat index can actually be lower at 100 degrees than it is for 95 degrees. For example, 95 degrees with a dew point of 78 will feel significantly hotter than 100 degrees with a dew point of 66.
I’m old enough to remember when IAH opened and the weather station moved from Hobby to IAH. We were told then that summer temperatures would likely measure hotter and winter likely colder than they would have at Hobby.
Excellent explanation of something I’ve wondered about. Thank you so much!
I live near Jersey Village and usually match IAH very closely for high temps. I got to 99.1 on Tuesday. And according to Wunderground, IAH also maxed out at 99. https://www.wunderground.com/history/daily/us/tx/houston/KIAH/date/2025-7-22
Perhaps it hit 100 briefly between hourly snapshots.
Great explanation. What I think about this is just my opinion. Why do we as professionals in one subject or another, have to explain this to individuals who have no clue about how things work. It’s a down right shame. We NEVER growing up or our parents had some many opions on everything all the time.
Really appreciate you and your staff, to bad you have to spend your valuable time on explaining such trivial things. Conspiracy everywhere! 😆
Exactly.
Shame! Shame! Shame!
Current observation based on the source of the readings: IAH-94°F, downtown Houston-92°F.
I feel like the IAH debate is essentially just, “Houston is a big city and results may vary across it” in different words. 😂 Thank y’all as always for the great post.