Question: Does the prohibition of Muktzeh apply to snow that falls on Shabbat?
Answer: Maran Ha’Bet Yosef (end of Chapter 310) quotes the Shiboleh Ha’Leket who quotes Rav Tzemach Gaon who writes, “One may wash with or drink rainwater that fell on Shabbat although there were no clouds the day before.” This means that rain that falls on Shabbat is not Muktzeh and thus, rain which fell before the onset of Shabbat is certainly not Muktzeh.
This can likewise be inferred from the ruling of Maran Ha’Shulchan Aruch (end of Chapter 338) that if one places a vessel in one’s home in a place where rain is leaking into the house, the vessel with the water inside. This implies that the prohibition of Muktzeh does not apply to rainwater.
(The root of the discussion whether or not Muktzeh applies to rainwater is due to the prohibition of “being born” or coming into existence on Shabbat, such as an egg laid on Shabbat, which cannot be eaten until Motza’ei Shabbat. We shall not delve into this law at length because halachically speaking, the Gemara (Eruvin 46a) rules that the prohibition of Muktzeh does not apply as the result of an object’s coming into existence on Shabbat. Nevertheless, some rule that water dripping from an air conditioner on Shabbat does retain a Muktzeh status. See Maran zt”l’s discussion in his Chazon Ovadia, Shabbat-Part 3, page 144.)
Hagaon Harav Tzvi Pesach Frank zt”l, late Chief Rabbi of Jerusalem and the leading halachic authority of the generation for over fifty years, writes in his Responsa Har Tzvi (page 288), as follows: “On Shabbat, Rosh Chodesh Adar of the year 5717 (1957), there was heavy snowfall in Jerusalem. I was asked if the snow is Muktzeh and forbidden to move. Clearly, snow which fell on Erev Shabbat is not Muktzeh in and of itself as the Gemara in Masechet Shabbat states, ‘One may crush snow into water on Shabbat.’ Since snow is innately non-Muktzeh, the same law will apply if it falls on Shabbat and it shares the law of rain which falls on Shabbat and is not Muktzeh.”
Regarding shoveling snow with a shovel or any other tool (when there is an Eruv and carrying is permissible), when the ground under the snow is layered, such as asphalt or cement, although there are those who rule stringently and forbid moving the snow aside because this is a great bother on Shabbat, nevertheless, Maran zt”l (ibid.) rules that there is room for leniency in this regard, especially when one may slip and fall as a result of not shoveling. It is likewise permissible to spread salt on the snow so as to cause it to melt faster.
Summary: Snow which falls on Shabbat may be moved and may be used to drink. According to the letter of the law, one may shovel snow from the entrance to one’s home on Shabbat (as long as there is an Eruv in the area without which nothing may be carried).
Nevertheless, this applies only to moving snow on Shabbat. However, pressing snow into snowballs, snowmen, or igloos is similar to the forbidden work of building on Shabbat and several Poskim who prohibit this rule this way based on the wording of the Rambam that “gathering piece by piece and sticking them together until they become one unit is similar to building.” Thus, one should not act leniently regarding this issue.