Hello and welcome to the forum!
Although this reply is a year late, I figured this can help other guests and members who might have the same query. Anyway, right now, the weather in Mumbai is quite rainy. It is considered as monsoon season as it's the month of July. Temperatures range from 27°C to 29°C.
So let us start with the monsoon season, which is from June until late September. Although it rains a lot, humidity also rises in the region. The main issue with the monsoon season is that Mumbai gets flooded, a lot. The lush greenery during this season is quite amazing though. But generally, tourists are advised to avoid the region in the rainy season.
Now, let us go to the winter season, which is from October to February. Temperatures range as well but it can go as low as 17°C. The climate during this time is pleasant for sightseeing as compared to other seasons. Humidity lessens as well which is always a good thing. This is the peak tourist season as well.
The last season is the summer season, which is from March to May. Temperatures are the highest at this time sometimes even exceeding 40°C. Unless you're from a tropical country and used to such harsh and hot climates, it's not advisable to visit Mumbai during the summer season.
Generally speaking, Mumbai experiences a humid climate all-year round. It experiences moderate temperatures due to the proximity to the coastal areas, but it also has a humid climate because of the same reason. That's why the winter season is the best time to visit Mumbai when temperatures are a bit colder and humidity isn't as strong.
I hope this helps!