Ruling on combining the two prayers during rain

Question:
What is the criterion for combining the two prayers during rain, or during the time of rain?

Answer:
When an excuse arises, one combines the two prayers, Zuhr and 'Asr, and Maghrib and 'Isha', just as the sick person and the traveler do. Likewise, heavy rain, according to the most correct of the scholars' opinions, allows combining Zuhr and 'Asr. Some scholars say that Zuhr and 'Asr are combined during the day if there is no hardship, but the correct view is that there is hardship if the rain is heavy and the markets are flooded with water, making it difficult for people to go out for 'Asr. If they combine Zuhr and 'Asr by advancing them, there is no harm, just as with Maghrib and 'Isha, and just as with the traveler and the sick person, whether they combine at the beginning of the time or in the middle of the time.
The important point is that if there is something that causes hardship for them, such as being in the mosque, and heavy rain occurs, and the markets are damaged by mud and water, they may combine, and there is no harm. If they do not combine, they have an excuse to pray in their homes due to the presence of rain in the markets and the presence of mud. They have an excuse to pray at home. If they combine, there is no harm, and if a Muslim prays at home because of the excuse, there is no harm.

Question: Does this mean that the presence of rain is a condition?

Answer: Rain, or mud, or slippery ground.