BeChukotai

The following is the explanation of the Ramban on the first pasuk of Bechukotai:

The blessings of Bechukotai begin with rain because seasonal rain makes the air
pure and the springs clear and this leads to good health. Rain causes all produce to be increased and improves the quality of the environment. If the ecology of the world were at the ideal level due to abundant rain at the right time then people would not get sick and would live naturally for a very long time. Thus, rain is the greatest of all blessings and is therefore given priority of all the blessings.

We forget sometimes that people don't die from old age. People die from illness. Adam made a mistake that brought death into the world. Adam lived to nine hundred and thirty! The Ramban says that with good health we could all live that long.

Rabbi Gavriel Zinner writes his sefer Nit'ei Gavriel that rain in between Pesach and Shavuot brings great healing for all illness. The Imrei Pinchas writes that it is therapeutic to stand in the rain between Pesach and Shavuot with ones head a bit exposed to the falling drops and even to open one's mouth and allow the rain to fall into it. The late Puppa Rebbe spoke of his father, the VaYaged Ya'akov, following this practice. The Segulat Yisrael writes that this rain is especially helpful on Lag Ba'Omer and that having rain on this day is a siman bracha -good sign.

May we be blessed with continued rains of blessing and continued health.