Yevamot 72A

ואיבעית אימא: משום דלא נשיב להו רוח צפונית. דתניא: כל אותן ארבעים שנה שהיו ישראל במדבר לא נשבה להם רוח צפונית.

And if you wish, say instead that it was because the north wind did not blow for them, and the hot weather was likely to lead to medical complications following the procedure. As it is taught in a baraita: All those 40 years that the Jewish people were in the wilderness, the north wind did not blow for them.

מאי טעמא? איבעית אימא משום דנזופים הוו, ואי בעית אימא דלא נבדור ענני כבוד.

The Talmud asks: What is the reason that this wholesome wind did not blow all those years? If you wish, say it was because they were under censure following the sin of the spies and were therefore undeserving of this salutary wind. And if you wish, say instead that it was so that the clouds of glory covering the Tabernacle should not disperse.

אמר רב פפא: הלכך יומא דעיבא ויומא דשותא ⁠— לא מהלינן ביה, ולא מסוכרינן ביה. והאידנא דדשו בה רבים, ״שומר פתאים ה׳״.

Rav Pappa said: Therefore, learn from here that on a cloudy day or on a day that a south wind [shuta] blows, we may neither circumcise nor let blood [mesokhrinan], owing to the danger involved. But nowadays, when many are accustomed to ignoring these safeguards, the verse “YHWH preserves the simple” (Psalms 116:6) is applied, and it is assumed that they will come to no harm.

תנו רבנן: כל אותן ארבעים שנה שהיו ישראל במדבר, לא היה יום שלא נשבה בו רוח צפונית בחצי הלילה, שנאמר: ״ויהי בחצי הלילה וה׳ הכה כל בכור וגו׳״ מאי תלמודא? הא קא משמע לן דעת רצון מילתא היא.

A baraita states: All those 40 years that the Jewish people were in the wilderness there was not a day in which the north wind did not blow at midnight, as it is stated: “And it came to pass at midnight, that YHWH struck all the firstborn in the land of Egypt” (Exodus 12:29). The Talmud asks: What is the biblical derivation? How is it derived from this verse that speaks of the exodus from Egypt that a north wind blew at midnight during the 40 years that the Jewish people wandered in the wilderness? The Talmud answers: This comes to teach us that a time of favor is a significant matter. Since midnight had once been a time of divine favor at the beginning of the exodus from Egypt, it continued to be a time of favor throughout the 40 years that the Jewish people sojourned in the wilderness.