It seems to have been a cooler spring than it has been in the past—we just recently (May 23rd) hit 90 degrees for the first time this year (as measured at DFW Airport). For some reason, I always think that our really hot weather (100 degrees +) begins in late May/early June, but actually it is late June/early July. Most of our 100 degree days in the DFW area (15.2 of our average of 18) occur in July & August.
Thanks to the internet and the National Weather Service, following is some more information concerning 100 degree days in the DFW area:
- Average date of first 100°F: July 1
- 2019—July 30th
- 2018—June 22nd
- 2017—June 23rd
- 2016—July 22nd
- 2015—July 26th
- 2014—July 13th
- Average date of last 100°F: August 26
- Earliest occurrence: Mar 9, 1911 (100°F)
- Latest occurrence: Oct 3, 1951 (106°F)
- Average number of 100 degree days: 18
- 2018—23 total 100 degree days
- 2017—10 total 100 degree days
- 2016—19 total 100 degree days
- 2015—15 total 100 degree days
- 2014—15 total 100 degree days
- Most in a calendar year: 71 (2011)
- Fewest in a calendar year: 0 (1973 & 1906)
- Most consecutive: 42 (1980)
- Most in a month: 31 (July 1980)
Average number of 100 degree days by month
- May—0.2 day
- June—1.2 days
- July—6.0 days
- August—9.2 days
- September—1.0 day
In the record breaking year of 2011 when we had 71 days of at least 100 degrees, we had our first 100 degree day on June 13th and our last one on September 29th—what a summer to remember! July was brutal that year with all but one day reaching 100 degrees. For those of you who were in DFW in 1980, every single day in July reached 100 degrees!
As you can imagine, these 100 degree temperatures can create problems for swimming pools even when a routine swimming pool maintenance program is followed. Two of the most common pool problems that pool owners experience this time of year due to the heat are cloudy water and algae.
Cloudy water due to water chemistry imbalance—Low sanitizer (chlorine) levels or high pH levels (above 7.6) can cause cloudy water. Professional pool cleaners know the importance of keeping the pH toward the lower end of the ideal range of 7.2 to 7.6—as chlorine is much more effective as those lower pH levels. If you have cloudy water and suspect that it is a water chemistry problem, simply test the water and treat as recommended or better yet, take a pint of your pool water to a professional pool store. They will be glad to analyze your pool water and recommend treatment.
Treating algae in pools—Most algae can be prevented and can usually be blamed on low sanitizer (chlorine) levels. It is much easier and less expensive to prevent algae than it is to treat it. Many pool owners in the Denton area use an algaecide weekly as a preventive measure. This, along with brushing the pool regularly, is very effective in preventing algae.
There are several types of algae that are common in this area. They are as follows:
- Green algae—is either free-floating or attaches itself to the pool surface.
- Yellow (or mustard) algae—usually found in low flow areas of the pool.
- Black (or blue-green) algae—forms a root system which makes it difficult to remove.
Treatment varies with each one of these types of algae, but it usually consists of increasing the sanitizer level, using an algaecide, and brushing the pool.