Bill's translation is probably the closest but I would group the 'ko' and
'yuki' together to produce the word 'koyuki', meaning 'a light fall of snow' or
'a light snow'. This gives the impression that the flowers are similar to a
light summer snowfall.

Excellent. But these are good size flowers, more the size of a snowball. LOL.
However, if they remind the registrant of a light summer snowfall, that's fine
with me.
As regards your request for the placement of stress on particular syllables,
my comment would be that the Japanese language does not use stresses but,
instead, uses rising and dropping inflections.

So how do I, with round eyes, pronounce Natsukoyuki without breaking my teeth?
Arigato
Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)