Is there a rule that immersing in a Mikvah must be done during daylight? If so, why?

Answer 1

The mikveh must comply with a number of precise halakhic [Jewish legal] qualifications. The mikveh must be built into the ground or the structure of the building. It must hold a minimum of 24 cubic feet of water--200 gallons. The depth must be such as to enable an average adult to stand upright and have the water reach at least 11 inches above the waist, so that immersion can be performed without backbreaking contortions.

The water must originally have been transported to the mikveh in a manner resembling the natural flow of waters. The general practice is to build cement channels at the sides of the mikveh roof, which will enable rainwater to flow directly into the mikveh. Done right the first time, with the required initial amount of water, other piped waters may be added later in whatever quantities and at any time, and the mikveh will still retain its religious validity.

The waters must be stationary and not flow (not even the flow caused by a filter) while the mikveh is in use. The water, by all means, should be chlorinated to assure its meeting the highest standards of hygienic cleanliness. (While the chlorinated water may be somewhat discolored, it does have to retain natural water color.)

Water deriving from a natural spring is considered a valid mikveh if it complies with halakhic conditions. Also quite proper is immersing in the ocean, where there is no mikveh available, given the satisfaction of certain halakhic conditions.

The ceremony must take place on a weekday [and not on Shabbat, the Sabbath] and during daylight, as do all other Jewish court procedures. In cases when a full circumcision has to be performed (unlike the touch of blood for previously circumcised males), enough time will have to elapse to be certain that the wound has healed completely.

The only assurance that the immersion will accord with halakhic requirements for a male convert is the presence of the rabbi at the mikveh; a female is to be accompanied by a person familiar with the practice, such as a rabbi's wife, the mikveh escort, or a very knowledgeable friend who herself uses the mikveh.

The body must be thoroughly cleansed immediately before the immersion. The convert should be careful that there are no adhesions such as bandages, Band-Aids, or ointment; that the hair is thoroughly brushed; the nails of the hands and feet are pared; and that no traces of cosmetics or nail polish remain. The whole body must be immersed at one time, not sequentially, and the submerging must be total, without even a single hair remaining above the water.

Answer 2

I don't think so, except it'd be pretty inconvenient going at night! Plus, it's probably a public thing is it not? Like a swimming pool? So It may well be closed at night. But I don't see why it'd be a problem if you mean dark in daylight hrs e.g. winter.

Answer 3

No. But for impurity (which people don't care about nowdays), you may still be impure until the sunset, but that has no practical application unless you go on Temple Mount.

Answer 4

As long as the milkbath is warm it doesn't matter.