This is the 821st most frequent German word.
extrem
"Extrem" in German means "extreme" in English.
Here, 'extrem' is used as an adverb to describe the intensity of the adjective 'heiß' (hot).
Das Wetter ist heute extrem heiß.
The weather is extremely hot today.
In this case, 'extrem' is modifying the adjective 'hohe' (high) to convey a high degree or intensity.
Es gibt extrem hohe Berge in dieser Region.
There are extremely high mountains in this region.
Here, 'extrem' amplifies the sense of risk associated with the adjective 'riskant' (risky).