A seven-day heatwave is likely in the Miami Valley this week.
The latest 90-degree temperature in Dayton was recorded on Oct. 15 in 1899. Since 1896, there are four years the high temperature never reached 90 (2004, 2000, 1958, 1934).
Typically we see the most 90 degree days in July. Since 1990 there’s been a total of 7 days at or above 90 degrees in May, 95 in June, 190 in July, 129 in August, 62 in September, and 2 in October.
Temperatures heat up in June as we reach a peak of 14 hours, 59 minutes, and 20 seconds of Daylight around the summer solstice either June 20 or 21.
On July 9, we begin losing more than a minute of daylight each day.
Check out this relationship between 90 degree days and sunset times.
The earliest Dayton recorded the last 90-degree day for the summer was on July 8 in 1971. Then the sunset happens before 9 pm on July 21.
The average last 90-degree day is Sep. 4. The sunset is before 8 p.m. starting Sep. 6.
The latest we’ve felt the 90s is Oct. 15. The sunset is before 7 p.m. by Oct. 13.
By October 15 we only have 11 hours and 9 minutes of sunlight. We are losing sunlight at a rate greater than 2 minutes a day. The lack of sunlight makes it difficult to reach 90 degrees.
The weather pattern also plays a role. Right now we are seeing a nice ridge develop across the eastern half of the United States. This will stick around into the weekend. A cold front will bring relief as we start September.