July 7th, 2009
Austin’s 100-Degree Days
Visualizing the heat.
Every season has its symbols and traditions. Bluebonnets mean spring. Oxblood lilies, fall. And when I begin a fist-shaking litany of complaint about the heat, the drought, and how I want to move into a high-rise downtown and never garden again, my husband knows it’s summer.
“This is different.” I say. “Summer wasn’t always like this.”
My husband rolls his eyes.
Despite your visions of Texas as a tumbleweed filled barren desert, central Texas is not anything like the landscape from a John Wayne movie. (This is the Monument Valley in the Painted Desert of Arizona…a true desert.)
This is not central Texas.
I know it’s pointless to keep acting as if nothing is different–to plan and plant and use water as if nothing has changed. By any measure, there is nothing normal about this heat: not the number of days, the time of year we’re having them, or the high temperatures that Austin has experienced the last two years in this critical-stage drought.
I come from the group of people who think that if they can only explain something well, then everyone will understand the obvious. Thus, I’m compelled to quantify my pain.
So I charted all the 100 degree and hotter days Austin has had from 2000 to 2009. I used the official temperatures from Camp Mabry (not ABIA or my neighborhood weather station). I wanted to put them all on one bar graph but there are so many I ended breaking them up by year. The graphs are wide (you have to scroll) which is why they are on a separate page and not embedded into this post.
How hot is it supposed to get?
I started the chart with 2000 for a couple of reasons. First, as I understand how the “average” temperature is calculated, the weather service takes an average over 30 years of the 3 previous decades. So the average we’re working with now is from 1971-2000. This is a cooler, wetter period than Austin in the 1950s or in the current decade. This decade is resetting what’s “normal” for Austin.
But the year 2000 was also the September that broke all previous high temperature records in one horrible week. So I felt compelled to start with the trendsetter for this decade.
- 8/31: 107°F. Record high for the date. 33 days 100 or above.
- 9/01. 107°F. Hottest September temperature in history.
- 9/02. 107°F.
- 9/03. 108°F. New hottest September temperature in history.
- 9/04. 110°F. Hottest temperature in Austin history.
- 9/05. 112°F. New hottest temperature in Austin history. Hottest week in Austin history.
Altogether, the year 2000 had 42 days 100° or hotter over the summer. At that time, it was in third place. 2008 has already knocked it out of the record books, taking third place with 50 days. [2009 broke the record for third place again on August 10, with 51 days…and counting.]
When is it supposed to get hot? When is it supposed to stop?
In the 1990s, I’d start worrying about rain around Father’s Day. But I didn’t start moping about the heat until after the Fourth of July. Back-to-school rains would bring relief and temperatures would cool down to the 90s in September.
The statistics bear me out. While we might have the odd 100° day in June or even the last couple of days of May, generally the heat doesn’t arrive in Austin until July and it’s most prevalent in August.
Even in record-breaking 2000, the first 100° day wasn’t until July 12th. Contrast that with 2008 when the first 100° day was May 20th…almost two months earlier! July 12, 2008 was the twenty-fourth day of 100° heat last year. This year we started a little later than 2008 (June 13th) but the daily temperatures have been much higher. As of July 5th, 2009 Austin has had twenty 100° or hotter days. To put it another way, on this date (July 7th) the year 2000 had forty-two more days of 100° heat to come. What do you think is in store for 2009?
On average, the heat ends in August. But the year 2005 was also a record-breaker. The 100° days didn’t start until June 30th. Then there was a break from mid-July to mid-August. It looked like a normal September until the last week when Hurricane Rita slammed into Texas and Louisiana. No rain reached Austin but it had a crazy effect on our temperatures.
- 9/25. 107°F. Previous record 97°.
- 9/26. 107°F.
- 9/27. 103°F.
- 9/28. 106°F.
September 2005 is now the hottest September on record. And Austin shows the potential for 100° days from May 20th to September 28th: more than four months.
How many days is it supposed to be hot?
The average number of 100° days in Austin is 11. So, 2009 has already almost doubled the average.
This decade has had some cool years. After 2001 broke the record of 100 degree days or more in a row (19 in 1925; 21 in 2001) a record-breaking rainfall at the end of August ended the heat’s hold for 3 years. Over the 3-year period of 2002, 2003, and 2004 the combined, the total was only 9 days. After the devastating August of 2006, we had a gloriously abnormally, cool and wet year of 2007: only three 100° days that year, in August with a max temperature of exactly 100°. Ah, those were the days.
Then came 2008–pushing its way into the record books with the third most 100° or hotter days on record: 50 (breaking the third place record set in 2000 of 42).
With a record-breaking week of June temperatures and twenty 100° days already under our belt, 2009 looks grim.
Update: July 10, 2009
This just in from Jim Spencer at KXAN.
“[Austin] topped 100 degrees for the 23rd time this summer–eclipsing the number of 100 degree days one year ago today, at which point we were about halfway through what equalled the hottest summer on record in Austin…It’s not out of the question that we reach 100 degrees or hotter every day for the rest of July! If that happens, it will be become the longest stretch of consecutive triple digit days on record.”
Update: July 14, 2009
Lake Travis Shrinks to a 25 Year Low. The lake is dropping 1.5 feet a week. The current lake level is just above 640 feet; this is the fourth lowest level on record. The lowest level ever is August 1951 when it sank to 614.18.
Update: August 10, 2009
Today we break last year’s record of 50 triple digit days. Today is day 51 and we are now in third place behind 1925’s 69 days and 1923’s 66 days. Per KXAN’s Jim Spencer,
“As it stands today, this summer is by far the hottest ever recorded, with an average temperature of 88.3 degrees since June 1st. That is more than 1 full degree higher than the previous record set last year!”
Update: August 13, 2009
The “trigger point” has been reached for Stage 2 Drought Restrictions which will go into effect on August 24, 2009. The combined storage of lakes Buchanan and Travis has dropped to 900,000 acre-feet.
Update: September 3, 2009
We hit our 68th and final triple-digit temperature of 2009. We come within one day of tying the all time record (69 in 1925). Glad it’s over but it seems unfair to suffer so much and not get the record.
“From a vegetative standpoint, I think we’re going to be seeing the impacts of this drought for many years to come, many of our old native trees around this area are severely stressed during this drought.” — Bob Rose, LCRA meteorologist
by M Sinclair Stevens