I understand, Vlad. Hot and humid are not good, any time.

Neither hot nor soap are good for BP guns. Most soaps contain
salt, while many are mild forms of acids that might not
be neutralized, completely.
Yes - I know, so many books say to use soap and hot water.

They are wrong.

It is not that I am right - I am not claiming to be right.

Holland and Holland of the UK wrote a letter to my friend, telling him that cold or at the most, tepid water is all that is needed - no soaps (salt and some with acids) & no hot water as it causes flash rusting in many BP gun steels.
Flash rusting damage is accumulative. It in itself, is a cancer. THAT, I have observed in a friend's rifle - always used soap - always used almost boiling hot water. His bore was finely pitted, one end to the other after only about 6 years of shooting that rifle Taylor built him. He would not even have a beer before cleaning his rifle and did it EXACTLY the same every time. Boiling hot water and soap. (seems to me, the detergents are acidic). He ALWAYS cleaned his rifle immediately after shooting. We'd have a beer or two first. His bore started fouling, holding fouling and then found it pitted, one end to the other. We had to lead-lap it twice to return it to usefulness again. It's still a bit harder loading than it used to be. We all use grossly oversize combinations because they are more accurate than looser combinations.

ALL my barrels come off for cleaning, whether they are pinned to the stock, or secured with wedges.
The breech goes into the water and water is drawn up into the bore with a doubled flannelette patch. The jag is filed so a doubled patch fits perfectly.

I clean my pistols the same way as I clean my long guns.

After cleaning and drying the gun, H&H says to spray LIBERALLY all parts with a water displacing lubricant. I chose WD40 and have been using this since 1974, when I read that letter from H&H to my good and close friend and double collector, Wil Tompson of Smithers, now left the range. Amsoil Water displacing Lubricant is even better, but I can't remember what it is called.

Heat and humidity are tough on guns.

I spray it down the bore until it runs out the nipple seat, or vent. A clean dry patch is doubled and placed on the muzzle, then this is shoved down the bore with a HARD stroke. This stroke blasts excess WD40 out the vent or nipple seat, subsequent pumps discharge more excess WD40 out the vent. This also carries with it, ANY residual moisture and is the reason for using copious amounts of it. WD40 is cheaper than gun part replacements.
I buy it by the gallon can - for something like $27.00. That gallon lasts me a year. That money spent is cheap insurance.

Here, due to low average humidity, no further rust preventatives must be used. In areas of high humidity, better rust prevention might be needed. Break-Free CLP, invented to keep M16's working in VietNam, might be a good one or not, I do not know.