At the end of the parsha this week Moshe tells the Jewish people that they should remember this day that they are leaving Egypt and not eat chametz, etc.. He then says in 13:4, "היום אתם יוצאים בחודש האביב" - This day you are leaving in the month of the spring.
Rashi points out that we already know when they are leaving, so why does it need to be siad specifically in this fashion?
Rashi explains that it is telling us the great chessed that Hashem did for them that He took the nation out in the spring when the weather is pleasant, rather than in hot or cold weather when it would have been less pleasant.
My question is, why is this such a big chessed - we know the Jews were encircled and protected by the ananei hakavod - the clouds of glory - and they were a form of climate control. We know they were not affected by the weather and elements because of the clouds. So who cares what the weather was like when they left?
My initial thoughts are that while it is true that when they left Egypt they were not affected by the weather, however they did not know that would be the case. They knew they were about to leave Egypt and maybe they were nervous that they were running out in the heat or cold. So Moshe, to allay their concerns told them that Hashem scheduled it as a chessed that they are leaving in pleasant weather. Even though the facts are that it would not matter later. It was to calm their fears.
Answer: I still think there might be something to the above answer I suggested, I now have a better answer.
My 7 year old son gave me an answer that I think is correct. I asked the question at the shabbos table and he answered right away.
The ananei hakavod were only put into place when bnei yisroel travelled from Sukkos, which at the beginning of parshat B'Shalach we see was on the second day after having left Egypt. The first day they travelled from Ra'amses to Sukkos and did not yet have the clouds of glory or the pillars of fire.
That being the case, they needed the good weather for that cloudless day.