Re: When a plane flies through a cloud, does it get wet?

Sometimes.

Clouds are made of water droplets or small ice crystals.  

When a plane flies through a cloud that is made of water droplets it must
hit the droplets.  However with jet aircraft they do not get very wet or
stay wet for long.  They are going very fast and they tend to be fairly
smooth so the water doesn't stick very well.

It is not unusual to see small droplets of water running up the windscreen
when flying through cloud.   If the cloud is very thick and the droplets
are large the sound of the water hitting the cockpit windows can also be
very loud.  However in cloud that is thin and with small droplets you can
often not see any water hitting the windscreen (even though there must be
some because that is what cloud is made of).

We also try to avoid cloud that has a lot of large water droplets in it. 
The water droplets are held in the air by updrafts.  So cloud that has lots
of large water droplets must have large updrafts.  These clouds will be
very turbulent to fly though.  Our weather radar works by detecting the
water droplets in cloud.  So we get strong returns on our radar set from
clouds with lots of water.

I have flown through thick cumulus cloud that contains a lot of water.  It
is loud, bumpy and the aircraft is definitely getting wet with a lots of
visible moisture running up the windscreen.

The wispy cloud that planes often fly though either has very small water
droplets or very small ice crystals.  These do not make the aircraft
noticeably wet, though as I said earlier there must be some water hitting
the aircraft, it is just a very small amount.

Martin Smith