Miami broke its all-time heat record for June, but no warnings were issued.
On the same day, a high temperature of 91 degrees was recorded in Topeka, Kansas, and a heat advisory was issued.
What happened? Isn't 98 degrees hotter than 91 degrees?
Yes, but every National Weather Service (NWS) office has different criteria for heat advisories and excessive heat warnings that take into account a region's topography, climatology and potential urban heat island effects.
For example, Miami was really hot on Tuesday but did not meet the technical requirements for a heat advisory or warning.
In order to receive a heat advisory, Miami must have a heat index value of 108 degrees or higher for at least two hours. For an excessive heat warning, the heat index needs to reach 113 degrees or higher for at least two hours.
The National Weather Service
says a heat advisory means people can be affected by the heat if they don't take precautions. An excessive heat warning means people could be "seriously" affected
The heat index is a measurement of how hot it feels to your body when you factor in both relative humidity and the actual air temperature. One limiting factor, however, is that the heat index is calculated in shaded locations, not direct sunlight, which can feel as much as 15 degrees warmer