Generally not comparable; comparative and superlative forms are rare and often considered incorrect.
Translations
arctiqueRelatif à l’Arctique; par extension, très froid. The arctic winds made it difficult to stay outside for long.
Les vents arctiques rendaient difficile de rester dehors longtemps.
glacialS’emploie pour insister sur un froid intense. The arctic winds made it difficult to stay outside for long.
Relating to the regions around the North Pole. The arctic landscape is home to polar bears and seals.