Mild freeze overnight with daytime temps quickly climbing into the 40s equals no worries. Multiple days below freezing, or DRIVING in freezing weather will freeze your pipes.
Fresh water freezes soonest, grey water somewhat slower and black tank will probably only freeze right at the valve. A little bit of pink antifreeze and your grey and black tanks will behave themselves. During extended stays I keep pouring small amounts of pink into my drains.
If you have exposed half-inch fresh piping, give thought to rerouting it above the floor. PITA, yes, but this is your most vulnerable area.
If the days are mild, the nights can get quite cold without issue. I often camp in the low teens overnight without any special precautions for the tanks, apart from pink stuff. But if the next day if forecast to hover in the low 30s I start to make preps the night before. I'll turn on my tank heaters and locate my aux clamplight. If the night gets much colder than forecast, there is still time in the morning to hit your pipes with the clamplight.
For extended stays in cold weather, I'll put on a skirt. I'm talking about a tarp "skirt" around the chassis that keeps the wind from blowing under your trailer. With a clamp light carefully placed underneath, extended stays in the 20s have gone without issue.
Others on this forum have camped in seriously cold weather in Canada and the Dakotas. My own experiences are mild by comparision, but probably more germaine to the topic of overnight stops. Bottom line, Pink Stuff and a little situational awareness and overnights will go just fine. But keep an eye on that fresh line.
