In India, The best season or seasons for constructions would be post monsoon followed by winter i.e., from September to March. The quality of houses built post monsoon or in winter will have an edge over houses built in summer and during monsoon. From the Month September to March usually there are No Rains in India.
How Rains Effect Quality of Construction
If Precautions are not taken care of for rains, Rains often interrupt or delay the schedule and/or affect the quality of Construction.
Construction in monsoon has lot of inherited challenges. During rainy season concrete once poured should be covered immediately so that its not exposed to direct rain which damaged the finish and increase the water-cement ratio affecting the strength of concrete.
Also, defining construction joints gets difficult, if concrete activity stops abruptly due to heavy rain. The concrete pour can only be taken up after the poured concrete has reached the final setting time.
Also treating the set concrete and fresh concrete joint where preparing construction joint is not feasible to make.
Although Monsoon season / Rains actually helps in curing the concrete structure post hardening of concrete, the above mentioned issues negate the benefits of constructing houses in that season.
Why Post Monsoon is the Best Time for Construction Work?
RCC, masonry, flooring and plaster works achieve their potential service life when worked with best practices of construction and have a conducive exposure environment.
If there is any delay or lapses in curing (most neglected work but the most important activity in construction), a cool exposure environment would lower delayed/lapsed curing detrimental effects on structures. Temperatures of around 24+/- 5 Deg C are considered relatively cooler for Indian Environment.
Usually, hydration process of cement/concrete will be enhanced as water within the concrete. Curing is done to avoid this water to escape or evaporate. Curing has to be done till the concrete or mortar achieves required strength (which is 7-14 days).
During cooler climates water would be there for a longer period (won’t evaporate, due to hot weather) enabling hydration of maximum quantity of cement incorporated in concrete mix.
More the percentage of cement gets reacted with water more the strength of concrete/mortar is attained. Also concrete/mortar which is well hydrated will have refined and less pores, making structure more durable too.
The probability of concrete getting properly cured is higher in post-monsoon and winter season than in other seasons and is worse during summer season as water quickly dries up. This gives an edge to the houses that are constructed during post-monsoon and winter and make them to be of better quality and finish.
Construction is done in stages starting with RCC, then Masonry, then Plaster, then Tiling and Painting.
RCC works initiate a construction process. It is the main structural member of any building and need all the care to deliver a good quality end product.
RCC should start post monsoon and the later part of construction (Masonry,Plaster, tiling etc) can be scheduled later having less bearing on construction environment.
The above answer is specific to Indian environment and construction practices.