Linked from
The 18 pages that link to Heat wave, each with the reason it gives.
Subtropical ridgeRelated: Stable air beneath a persistent ridge can favor prolonged heat.
Death ValleyRelated: Extreme temperatures in the valley arise during persistent hot weather.
SummerRelated: Summer heat can intensify into dangerous extremes, especially in cities.
High-pressure areaRelated: A persistent high can suppress clouds and trap heat near the surface.