First thing to check here in a case like this to to make certain that the engine thermostat is working and is of the correct temperature rating.
A cold running engine is unable to quickly heat up the engine block and pistons so they can expand to the close tolerances they need for both efficient combustion, and to minimize combustion blow by past the rings and into the crankcase.
Water is a byproduct of the combustion process and the water will be blended into the lube oil and form an emulsion. This emulsion is usually a short lived phenomenon, but in cold running engines it can persist and build to unacceptable proportions.
Engines running at the proper hot operating temperature do not have a problem expelling the water from the crankcase oil because the water will evaporate out of solution when the lube oil heats up.
Engines that get cranked up and run only a few minutes at a time throughout a work day, never reaching full, hot, operating temperature are also susceptible to having water entrained crankcase lube oil, even if they have a good working thermostat of the correct temperature rating.
Engines that have a long dipstick tube, especially if the dipstick does not seal tightly to the tube, can give a false indicator of water in the oil when operated in cold ambient conditions. This is due to the long dipstick tube staying cold in the ambient air conditions and because the dipstick does not have a tight seal, the crankcase is allowed to vent out some blow by gases (which will contain water vapor) and some water will condense inside the dipstick tube. As the dipstick is withdrawn from the tube, it will drag some of this water/oil emulsion out with it. Dipsticks in these cases often take on a rusty appearance too.

A cold running engine can also account for a loss of power.