I recently shared some interesting numbers regarding the summer of 2016’s record-breaking heat in Cleveland and northern Ohio. Today, I figured I’d briefly look at where we are for the year to date. The mean temperature for the period January 1 through September 11, 2016 has been 55.9 degrees, which ties with 1921 as the 3rd hottest such period on record. The hottest such period occurred in 2012, with a mean temp. of 57.5F – a full 1.6F warmer than the present year. Second place occurred in 2010 with a mean temp. of 56.0F, just 0.1F warmer than this year. As can be seen from the data, there is a clear trend towards warming in recent years.



Figure 1. Mean temperature (average of daily high and low) for Cleveland, Ohio, from January 1 through September 11.

Maximum temperatures are often preferred by critics who claim the warming is due to the urban heat island effect. UHI typically impacts overnight minima much more significantly than daytime maxima. The data are not much different. This year is tied with 1952 as the 4th hottest based upon mean maximum temperature with a mean maximum temperature of 65.2F. The hottest year was again 2012 with a mean maximum temperature of 66.8F, followed by 1949 (65.7F) and 1955 (65.3F). Note the warmest maxima appear in the 1940s and 50s. It is worth noting again that the instrumentation was sited on the rooftop of the Terminal Building during those years. It’s likely that direct radiation from the dark surface of the roof was impacting the readings. Earlier years were also rooftop readings from various buildings downtown – however, the maximum temperatures are typically slightly lower in the downtown area due to its proximity to Lake Erie, which tends to temper the afternoon climate with frequent lake breezes.


Figure 2. Mean maximum temperature (average of all daily highs) for Cleveland, Ohio, from January 1 through September 11.

It will be interesting to see where 2016 ends up on the list of warmest years. But if history is any guide, there is a very good chance that it will remain in the Top 10. 2012 finished up as warmest on record for the full year. 1921 finished as #4. 1991 finished as #7. 1949 finished as #6. And 2010 finished as #9. Barring a chilly end to the year, we should remain near the top of the list. Stay tuned…