Every so often during the warm summer months, there can be an extended stretch where the heat cranks up. We call these times heat waves. Though heat waves are universally accepted to be rough stretches of heat, how long are they? And how hot does it have to get?

 

 

Heat waves can have different definitions in different regions. In the Valley, heat waves are a stretch of 3 or more consecutive days of 90°+ temperatures. Compared to average peak heating, mid-July’s highs in Youngstown get to 83°, so a heat wave would need to break at least 7°-10° degrees above average for a consistent period.

 

 

Heat waves typically occur almost exclusively during the summer months. Its peak occurs during July, aligning with the highest average temperature in our area. Heat waves can also occur during June and August, and much more uncommonly during early September. 

 

 

As long as highs get to 90°, heat waves can continue for as long as they can. Three and four-day heatwaves are common, happening about twice every three years, but longer ones are possible. The last time we had a five-day heatwave was in 2020. An unbelievable 12-day streak occurred to close out July 1940.

 

 

 

 

Though heat waves don’t cause the dramatic damage that other weather-related phenomena are responsible for, such as floods or tornadoes, their impact on those with existing health conditions makes it the leading weather-related cause of death in the United States. As such, the national Weather Service aims to issue heat alerts to communicate its impacts to the public. There are three levels, all conveying varying degrees of heat and timing. A heat advisory is issued when there is high heat in the area, but not enough to reach an extreme value. In Ohio, Heat Advisories are issued when the heat index, a value factoring in both temperature and humidity, is forecasted to reach 100°. This advisory value changes based on location. Parts of the Deep South get warmer regularly, so a heat index of 110° would then trigger a Heat Advisory. Further east, New England only needs a heat index of 95° in order for NWS offices to issue a heat advisory.

 

When conditions get even warmer, officials can issue Extreme heat products. An Extreme Heat Watch is issued when conditions are favorable for a locally extreme heat event, but its timing and occurrence are either uncertain or too far in the future. Once things are certain, though, an extreme heat warning can be issued, which is defined as life-threatening heat conditions that are either expected or occurring. The difference between a watch and a warning can be described as the process of baking a cake; a watch is issued once you gather all the ingredients on the kitchen table, while a warning is issued when all the ingredients are put together and actively baked in the oven.

How has our region fared with heat waves this year? About halfway through summer, the airport has registered two heat waves so far: one in June and one in July. The heatwave in June lasted four days, the longest since 2020, and also included a daily record hot day on June 24th. This marks the first year of multiple heatwaves since 2018. Our next chance for a heat wave is over the next few days, as we’re forecasting a high of 92° on Thursday, and while highs will be close, we are currently not expecting temperatures to eclipse 90° on Wednesday or Friday.