السلام عليكم My family is taking me camping for a few days, and the showers are located far and are difficult to use at night, and the water in the area is cold. In case of me having a wet dream before fajr, is it permissible to do dry ghusl/taymmum for ghusl and then perform ghusl in the daytime?

You can simply warm the water and use it, as long as you are able, because water is the origin and cold by itself is not an excuse when you can heat it (of course as long as there is no harm on you). If you genuinely cannot use the water without harming yourself, then yes, you may make tayammum and pray, and your prayer is valid and complete. When you are able during the day, make the ghusl for what comes after. So do not leave the prayer, and do not rush to tayammum while warming the water is still possible.