Quaestiones Naturales

Is it because they contain much spirit, by reason of their confusion and mixture with the air? And the spirit moving the humor sends it more upwards. Or is it because heat fighting against cold causes thunder and lightning? Whence it is that it thunders very little in winter, but in spring and autumn very much, because of the inequality of temper; and the heat, concocting the humor, renders it friendly and commodious for plants. Or does it thunder and lighten most in the spring for the aforesaid cause, and do the seeds have greater occasion for the vernal rains before summer? Therefore that country which is best watered with rain in spring, as Sicily is, produces abundance of good fruit.