Why does victor Frankenstein remember the thunderstorm from his childhood so vividly?

“From this day natural philosophy, and particularly chemistry, in the most comprehensive sense of the term, became nearly my sole occupation. I read with ardour those works, so full of genius and discrimination, which modern inquirers have written on these subjects. I attended the lectures and cultivated the acquaintance of the men of science of the university, and I found even in M. Krempe a great deal of sound sense and real information, combined, it is true, with a repulsive physiognomy and manners, but not on that account the less valuable. In M. Waldman I found a true friend. His gentleness was never tinged by dogmatism, and his instructions were given with an air of frankness and good nature that banished every idea of pedantry. In a thousand ways he smoothed for me the path of knowledge and made the most abstruse inquiries clear and facile to my apprehension. My application was at first fluctuating and uncertain; it gained strength as I proceeded and soon became so ardent and eager that the stars often disappeared in the light of morning whilst I was yet engaged in my laboratory.