Go up the waterfall in Ever Grande City and stay up there until you catch a Luvdisc and it holds a heart scale.(Then you can get as many as you want.)
Kill or capture the red Gyarados at the Lake of Rage.
In the heat gym
That would be Lavaridge Town, with the firey gym leader, Flannery. Beat her, and the Heat Badge is all yours! Your Welcome!
is there a scale used to measure the intensity of heat wave
heat scale
—Thermometers. —Celsius Scale —Kelvin scale —Calorimeter
in order to get heat wave first get a charlizard by going to the move tutor in Firered/ Leafgreen. But in Emerald Charkoal learns it at lvl 48.
Somewhere in olivine city you can find a angler who will give you it.
It is heat measured on the 'fahrenheit' scale.
The Scoville Scale
Emeralds are resistant to moderate heating.
if you beat game, you find heatran (heat pokemon) at treasure area and catch it