Can one wash dishes on Yom Tov with hot water at night if they may or may not be used the next day of yom tov. Meaning, a milchik meal is planned for the Yom Tov day meal, but since the day is long some may take fleishigs in the afternoon. Is this considered a sefek Tzorech Hayom?
If there is a possibility that the dishes will be used on the next day, it is fine to wash them on Yom Tov night.
The reason for this is that option of using the dishes on Yom Tov is also considered a “need of Yom Tov,” and it is permitted to make use of the hot water in order to give you this option.
Note that according to a number of poskim, it is permitted to wash dishes even for the sake of having a clean and tidy kitchen, even if the dishes will not be coming into use on Yom Tov.
The Shulchan Aruch (OC 323:6) and the Mishnah Berurah (323:26) write, concerning Shabbos, that it is prohibited to wash dishes when they are not required for used on Shabbos. However, if the household norm is for the sink to always be clear of dishes, and the sink being full of dishes is seen as clashing with the honor of Shabbos — and in this case Yom Tov — then it is permitted to wash the dishes.
The source for this leniency is Rashi (Shabbos117b), who writes that the prohibition of washing dishes is on account of preparation for weekdays. This implies that if the washing is not for preparation for weekdays, the act would be permitted. [There is certain debate about the position of Rambam in this matter.] The Maharshag, Orach Chaim, Vol. I, no. 61, writes explicitly that this is the case, and permits washing dishes for the sake of hygiene and cleanliness;Tzitz Eliezer, vol. 14, no. 37 concurs with the ruling.
The same concept will apply for purposes of Yom Tov. If washing the dishes is for the sake of Yom Tov — either for the option of using the dishes later on Yom Tov, or for the sake of having a clean kitchen etc., it will be permitted to wash the dishes for this purpose, even with hot water. The actual use of hot water for dishes is certainly “shaveh le-chol nefesh.”