There is no excuse for IIMC....ever. That being flying yourself into IMC conditions (being unable to maintain control of the aircraft by visual contact with external cues) while flying VMC.
That being said and I am not willing to debate that statement....a VFR only Pilot trying to build IMC and IFR Time with no notice....best hope your Life Insurance was paid up prior to flight.....no sense no good coming of your leaving.
A fully current and very proficient IFR Pilot will have problems coping with the event if the aircraft is not properly equipped....again invest in that Life Insurance.
The best and cheapest insurance policy....operating your aircraft in such a manner as you never go IMC in an inadvertent manner...ever.
In your trusty helicopter....use its unique capability to keep you out of trouble...slow down...hover if necessary...and fly at the speed that allows you to avoid ALL hazards.
In the context of this discussion....losing visual reference to the ground is the worst hazard possible.
If you can see and avoid wires, masts, trees, hills and mountains....why would you ever fly in a manner that does not allow for avoiding that really...really...really important hazard...losing sight of the surface?
You do not have to look at a weather forecast....I never had one in Iran, Burkina Faso, Alaska, and quite a few other places...to tell you how to fly once you are airborne.
The weather forecast can make hazard avoidance easy....marginal weather and forecast to get worse....weather below minimums....makes it simple....Coffee time.
Once you get airborne...if the weather deteriorates to below minimums for Take Off....HELLO! Land! Coffee time!
There is nothing we do in helicopter aviation that cannot wait (with the exception of perhaps SAR but even SAR Units have Minimums too!).
Why do you continue to fly in weather that if you knew existed along your route....you would not launch into?
My Hands are not clean....they are indelibly stained with guilt for having done exactly what I advocate against here.
I knew my limits and imposed the limitations that afforded me the ability to know when to call it quits before something bad happened.
The worst it got on occasions was not being able to get over a 35 foot high set of electric lines, or being unable to see my next Hover Spot....all of a hundred yards away....or relying upon a single wooden survey stake with some orange flagging as my sole visual reference atop a pinnacle/ridge landing site in a snow squall.
The Pinnacle thing scared me....for if that shaky wooden stake had departed its location...I would have departed into white out conditions in a VFR only MD 500.
The other life altering fright....was flying off the North Rim of the Grand Canyon in that same MD 500 (even the Airspeed Indicator had gone InOp....in very hazy conditions while holding up a big handful of VFR Map trying to figure out just where this Grand Canyon thing was....as I flew off the edge of the mile deep abyss...with only a few hundred feet of Vis.
There were some other frights including going IIMC in Rain while dropping water on an Ammo Bunker Storage Area Fire and winding up in the middle of a Monsoon Season Thunder Storm.
I survived....I went through some Guardian Angels who quit over not receiving Hazardous Duty Pay for their Duty Assignment.
Others of my Peers have not been so fortunate....I have attended far too many Funerals of Good Guys who were not as lucky.