Sun, Moon And Rain

At the end of the third aliyah in the parsha, the possuk says וּבַחֹ֙דֶשׁ֙ הַשֵּׁנִ֔י בְּשִׁבְעָ֧ה וְעֶשְׂרִ֛ים י֖וֹם לַחֹ֑דֶשׁ יָבְשָׁ֖ה הָאָֽרֶץ׃ .  Rashi says נעשה גריד כהילכתה בכ״ז, וירידתן בחדש השני בי״ז. אילו י״א יום שהחמה יתירה על הלבנה, שמשפט דור המבול שנה תמימה היה.  What is the significance of the fate of the generation of the Mabul lasting for a solar year?  This is a dumb question, but why is the solar year off from the lunar year by 11 days?  And why punish the people through rain of all punishments?

The sun and moon represent the spiritual and mundane aspect of a person's life.  Most people arew in a happier mood when it is sunny outside for the sun with its bright light represents warmth, comfort and peace.  It represents the spiritual side to a person.  The moon on the other hand, shines a dimmer light and it doesn't have its own light, it merely reflects the light of the sun.  This represents the darker side of an individual; the animalistic and mundane side of an individual that is concealed in darkness. It is the job of the person to take the light of his/her spiritual side and illuminate this weaker side.  In short, the sun and the moon represent the contestant struggle of the opposing forces within man.  That is why they are separated by 11 days.  In kabbalah, 11 is a number of the "evil forces" (see Sefer Yitzerah 1:4.)  When there is conflict between the "moon" of a person vs. the "sun" of a person, it can lead to danger.  It is a person's job to bring harmony to these two factions within himself and to avoid  the split of 11.

The Midrash Rabba Berashis (20:7) says אֵין תְּשׁוּקָתָן שֶׁל גְּשָׁמִים אֶלָּא עַל הָאָרֶץ, שֶׁנֶּאֱמַר (תהלים סה, י): פָּקַדְתָּ הָאָרֶץ וַתְּשֹׁקְקֶהָ, וְאֵין תְּשׁוּקָתוֹ שֶׁל הַקָּדוֹשׁ בָּרוּךְ הוּא אֶלָּא עַל יִשְׂרָאֵל, שֶׁנֶּאֱמַר (שיר השירים ז, יא): וְעָלַי תְּשׁוּקָתוֹ.  Rain is the connection between heaven and earth, between the גשמי  and the רוחני.  The generation of the flood had completely lost the balance between their two sides and could no longer continue existing in their current state of chaos.  Hence, the appropriate punishment was rain for it is rain that represents that coexistence of the  גשמי  and the רוחני that the דור המבול couldn't sustain.  That is why the waters lasted for a complete solar year for they failed to take advantage of their "sun" aspect, rather they were "lunar" oriented, hence they became loony.  "The term "lunatic" derives from the Latin word lunaticus, which originally referred mainly to epilepsy and madness, as diseases thought to be caused by the moon." ( https://en.m.wikipedia.org/wiki/Lunatic.)