Little night-time heat relief expected through the weekend
Nine of the last 10 days have reached or exceeded 90° in the Tri-Cities. Fortunately, though, there have been a lot of nights following that kind of heat that featured temperatures in the upper 50s and low 60s. That's pretty comfortable this time of year.
But as humidity rises a little bit this weekend, temperatures won't be able to drop that far. When dew points are higher, there's more moisture in the atmosphere. So, the temperature can only drop so far. When dew points are lower, the temperature has more room to drop.
With higher dew points tonight and through the weekend, temperatures won't drop as much. While this is nothing Earth-shattering, it's still not going to provide much relief from the daytime heat.
When most people drive into work, after 7 a.m. or so, the sun has already been up and started heating things up. In fact, most mornings this week have been in the 70s already as of 8 a.m.
Warmer nights are becoming more and more common, though. Especially the last three years, roughly two-thirds of our night-time lows are considered 'warmer than average.' That includes this year, and is a big part of why 2017 is touted as the 'second warmest year on record so far.'
Our friends at Climate Central have shown that, while there are natural fluctuations from year-to-year, the overall trend is nights getting warmer over the last 50 years.