Well...Based on past episodes, El Niño has a small and not very reliable cooling influence on summer temps in the contiguous U.S. It tends to have a bigger and more consistent impact on winter temperature and precipitation. We know that one reason we are seeing increasingly frequent occurrences of record heat in the U.S. is long-term global warming. Averaged across Texas, summer temperatures have warmed by a tenth of a degree each decade since 1895, mostly due to warming nighttime temperatures. 

https://www.ncei.noaa.gov/access/monitoring/climate-at-a-glance/statewi…

Scientists would have to do a kind of scientific study called an extreme event attribution in order to understand how much El Niño or other kinds of natural variability also contributed to any specific year's record heat.