Can it snow when it's 40 degrees?

No. If it is 40° on the ground, the freezing level, the 0° isotherm, will be at around 6000m and that is far too much warm air for snow not to melt - presuming there is even cloud to produce snow in such hot conditions.

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(character tax)

 It can be too warm to snow, it cannot be too cold to snow. 

Yes it will melt as soon as it hits the ground though.

I don't know how true it is, but I remember a TV programme asking how many days does it snow in the UK, and they said every day. As all rain starts as snow high up.

It can snow when it's 40°F at the surface providing the freeze level is no more than ~1000' above ground level.

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FALSE:  As a general rule, though, snow will not form if the ground temperature is at least 5 degrees Celsius (41 degrees Fahrenheit).

FALSE:  If 40F, then yes! It would fall as wet snow however, there would be a lot of liquid to it, due to melting in the lower atmospehre [sic].

FALSE:  No. Water freezes at 32 degrees, so you can't have ice above 32 degrees.

As a general rule, though, snow will not form if the ground temperature is at least 5 degrees Celsius (41 degrees Fahrenheit). While it can be too warm to snow, it cannot be too cold to snow. ... Because snow formation requires moisture, very cold but very dry areas may rarely receive snow.

40 degrees F or 40 degrees C?

If 40F, then yes! It would fall as wet snow however, there would be a lot of liquid to it, due to melting in the lower atmospehre, and the ground level would be too warm for any snow to acculamate.

Not when those degrees are Celsius

Yes, the snow is formed at a higher altitude where it is colder.