Significados de explainable reason en inglés

He lowered his head to the pillow feeling, for no explainable reason, strangely disquieted, only to rise again almost instantly exclaiming:

Tiring of this, I switched, for no explainable reason, to multiple-choice Adolf Hitler-Eva Braun jokes, but I had only completed one-

At 82°, 10,000 feet lower, it was regularly down to -47° in the night-time, and -30°during the day: for no explainable reason.