Acrylics drying to quickly

Hi all

I'm sure some of you are experiencing the same problem during this hot humid weather , that being your acrylic paints are drying to quickly especially if they are used straight from the tube....

If I was to use a retarder would this make blending much more easier such as painting clouds etc...

As yet I have not tried any method such as retarder as I just don't know how much to use and which is the best make to purchase, so I would value any suggestions a more experienced acrylic painter would do and use...