https://en.wikipedia.org/wiki/Mpemba_effect

I would say the science on this doesn’t seem very solid.

Yeah you can point to convection in the warmer liquid making heat transfer more efficient, to evaporation reducing the total amount of liquid, or to the fact that formation of ice isn’t solely tied to temperature falling below zero, and you can - under specific circumstances in which the conditions for the formation of the initial seed crystals are not ideal - have water below the freezing point but not yet frozen, but i think these are marginal effects at a large enough scale.

For practical purposes i would say it depends on what size the volume of water is, how much warmer the warm water is, and how cold it is outside (plus maybe some secondary factors like what kind of container it is in - closed, open, good thermal conductivity, bad, lots of surface area, etc.). Obviously if there is a big difference in temperature between the two volumes, the amount of thermal energy in the warmer water will be so much higher that even allowing for the possibility of some effects leading to more efficient energy transfer away from the warmer volume, you’ll still have the cold one freeze first.

I mean, the most simplified way to think about it is this: the warm water needs to first reach the temperature of the cold water before it can go to freezing. But by the time it does that the cold water will have already cooled down even lower. The formerly warm will now be in the same state as the cold water was initially, but the cold water has a head start. How can the warmer ever catch up if the rate of cooling depends only on the temperature differential between the liquid and the outside?

Of course this is an idealized model and in the real world you will have secondary effects (such as the evaporation i mentioned earlier - for instance if the temperature outside is just below zero and not some crazy low negative temperature, then maybe there is enough time for the evaporation of the warmer volume to make a difference), but can those make a big enough difference in your specific use case? I would suggest you just do the experiment yourself. Put two identical buckets of water out in winter when the temperature outside is below freezing, one with hot water one with cold, and see which one freezes first. My money is on the cold one, but trying it out is the only way to know for sure right?

Tangentially, consider that usually people are discouraged from drinking water from the hot tap.

So, many years ago, I worked at a fast food place in highschool and we had a big walk in 0°F freezer. One of my coworkers and a supervisor were debating this whole deal so the filled up two containers of water, one got and one cold, and put them in there.

Long story short, hot water froze faster. This was before the age of smartphones and such so we couldn’t pull up YouTube and other sources about it, but it can happen but the mechanics behind it are not entirely confirmed. Some theory is that heated water has less dissolved gas that can interfere with freezing, other are about volume either being lost, or the fact that hot water has a greater volume than cold water, either way meaning as it cools, its actually less overall volume of water. There’s other theories. I remember seeing this video about it some time ago but I haven’t watched it in a while.

https://youtu.be/SkH2iX0rx8U

Imo, I think it’s a combination of factors and that, evaporation in general will cool the rest of the liquid.Thays literally hot sweat works for humans. Water evaporates which pulls heat from your body. And hot water is gonna evaporated was faster in the cold weather. More evaporation is also reducing the total volume of water.less dissolved gas will allow it to not only evaporate faster but freeze quicker too.

But doing science at home it’s t too difficult either. Just measure out a cup of cold water from your tap, and a cup of the same hot water you would give to the animals. Set both outside in the same style and size of container, and check them ever 20 minutes or so. Way better and easier that guessing and hoping.

But all in all, I would also say if you have the option, you should used heated water bowls or put a heating element in their water container. Even a mall fish tank heater can prevent quite a bit of water from freezing. Might not keep it “warm,” but would keep “warm enough.”

it is better do drink warm water in the summer or the winter, because it is better for the digestive system and it needs less energy to warm up in the body