What is the lowest percentage humidity required for it to rain?

Question

Like is there like a "magic number" that the humidity has to be at least for it to be enough to cause rain?

So how come sometimes it's like 90% and it rains?!

Answer 1

It has been found out that condensation can take place in the atmosphere even when the relative humidity is around 70 percent provided abundant hygroscopic nuclei are available.
We know that condensation nuclei are required for the formation of cloud.Hygroscopic nuclei is one type of condensation nuclei.Nuclei like salt or sulphuric acid have affinity for water.Hence, particles of salt and droplets of sulphuric acid which are usually availble in the atmosphere are called hygroscopic nuclei.If they are abundant at a particular time, saturation may occur at a less humidity value.
Actually this is what is done in inducing an artificial rain.Salt is also added along with silver iodide and dry ice(frozen CO2) to bring down the saturation level and produce more clouds and later making the clouds to precipitate.

Answer 2

The relative humidity isn`t everything though. The relative humidity can be high and still not be humid. An example of that is in the winter. You need to look at the dew point. Once the dew point hits the 60's (for some people) its really humid. Once it gets the 70's and higher, its consider tropical airmass.

Answer 3

Yes the last answer is correct. It has to be 100% humidity / the air has to be fully saturated where the clouds are forming / cloud condensation level / at that particular time.

Answer 4

It has to be 100% in the cloud. Outside of the cloud, the % relative humidity is not pertinent, as the water is not condensing there.

Answer 5

100 per cent.
Anything less means there is moisture in the air.

Answer 6

100%, duh?