In Shemot 9:24, it says about the plague of hail:
"וַיְהִי בָרָד וְאֵשׁ מִתְלַקַּחַת בְּתוֹךְ הַבָּרָד כָּבֵד מְאֹד אֲשֶׁר לֹא הָיָה כָמֹהוּ בְּכָל אֶרֶץ מִצְרַיִם מֵאָז הָיְתָה לְגוֹי."
"The hail was very heavy—fire flashing in the midst of the hail—such as had not fallen on the land of Egypt since it had become a nation."
It sounds like the Torah is saying that prior to Egypt having become a nation, there was a time when fiery hail rained down on the land (otherwise, why mention that the hail had not fallen so since that time?). Are there any sources that discuss this ancient event?