Why do we stop saying Morid Hageshem?

Question

From Pesach until Succos, we stop saying mashiv haruach umorid hageshem in shemoneh esrei.
However, we would normally say it in the second blessing of the amidah, which is where we are only praising Hashem.
Therefore, why do we stop saying it just because we don't want/need it to rain, we are only praising Hashem for making it rain, not asking Him to?

Answer 1

The first several pages of Masechet Ta'anit deal broadly with this topic. From the opening mishnah, as well as a beraita cited in the Gemara, it seems that R. Eliezer agrees with you that there is no problem with saying morid hageshem all year round.

מאימתימזכירין גבורות גשמים רבי אליעזר אומר מיום טוב הראשון של חג ר' יהושע אומר מיום טוב האחרון של חג אמר לו ר' יהושע הואיל ואין הגשמים אלא סימן קללה בחג למה הוא מזכיר אמר לו ר' אליעזר אף אני לא אמרתי לשאול אלא להזכיר משיב הרוח ומוריד הגשם בעונתו אמר לו א"כ לעולם יהא מזכיר

WHEN DO WE [BEGIN TO] MAKE MENTION OF THE POWER OF RAIN? R. ELIEZER SAYS: ON THE FIRST DAY OF THE FEAST. R. JOSHUA SAYS: ON THE LAST DAY OF THE FEAST. R. JOSHUA SAID TO HIM: SEEING THAT RAIN ON THE FEAST IS A SIGN OF [GOD'S] ANGER WHY MAKE MENTION OF IT? THEREUPON R. ELIEZER SAID TO HIM: I ALSO DID NOT SAY TO PRAY4 BUT TO MAKE MENTION [IN THE WORD] ‘HE CAUSETH THE WIND TO BLOW AND THE RAIN TO FALL’ -IN ITS DUE SEASON. HE [R. JOSHUA] REPLIED TO HIM: IF THAT IS SO ONE SHOULD AT ALL TIMES MAKE MENTION OF IT.

(Soncino translation, capitals in original)

אמר לו ר' יהושע והלא גשמים בחג אינו אלא סימן קללה אמר לו ר' אליעזר אף אני לא אמרתי לשאול אלא להזכיר וכשם שתחיית המתים מזכיר כל השנה כולה ואינה אלא בזמנה כך מזכירים גבורות גשמים כל השנה ואינן אלא בזמנן לפיכך אם בא להזכיר כל השנה כולה מזכיר

R. Joshua said to him: Is not rain on the Feast a sure sign of [God's] anger? R. Eliezer replied: I too did not say to pray but to make mention. And just as one makes mention of the Revival of the Dead all the year round11 although it will take place only in its proper time, so too should mention be made of the Power of Rain all the year round although it comes only in its due season. Therefore if one desires to make mention all the year round he may do so.

(Soncino translation)

However, the Talmud immediately proceeds to record the opinion of Rebbe:

רבי אומר אומר אני משעה שמפסיק לשאלה כך מפסיק להזכרה

Rabbi says: I hold the view that when one ceases to pray [for rain] one should also no longer make mention of it.

(Soncino translation)

According to this opinion, praising God for rain is fundamentally linked with asking God for rain. Rashi there explains:

בימות החמה אינו מזכיר הואיל ואין זמנו

In the summer months we do not mention [rain] since it is not its time.

Eventually the Talmud presents the final ruling:

א"ר חנינא הלכך בימות החמה אמר משיב הרוח אין מחזירין אותו אמר מוריד הגשם מחזירין אותו בימות הגשמים לא אמר משיב הרוח אין מחזירין אותו לא אמר מוריד הגשם מחזירין אותו

R. Hanina said: Therefore, if in the summer one inserted [in the Tefillah the words], ‘He causeth the wind to blow’, he is not compelled to repeat [the Tefillah]; if, however, he said, ‘He causeth the rain to fall’, he is compelled to repeat [it].

(Soncino translation)

Here we conclude that saying morid hageshem all year round actually invalidates the prayer. Here Rashi explains:

לפי שהגשמים בקיץ סימן קללה הן מפני הקציר

For rain in the summer is a sign of curse on account of the harvest.

This apparently harks back to the debate between R. Eliezer and R. Yehoshua, with the conclusion that rain at the wrong time is bad, and thus it should not be mentioned during the times when its presence would be bad. As explained by Tosafot on the mishnah, R. Eliezer does not care about "a sign of curse" (which is why he allows morid hageshem all year round). But the Talmud's conclusion (which is followed in the codes) apparently follows the view that we do care about "a sign of curse".