  Measurements of the production of the standard model Higgs boson decaying to
a W boson pair are reported. The W$^+$W$^-$ candidates are selected in events
with an oppositely charged lepton pair, large missing transverse momentum, and
various numbers of jets. To select Higgs bosons produced via vector boson
fusion and associated production with a W or Z boson, events with two jets or
three or four leptons are also selected. The event sample corresponds to an
integrated luminosity of 35.9 fb$^{-1}$, collected in pp collisions at
$\sqrt{s} =$ 13 TeV by the CMS detector at the LHC during 2016. Combining all
channels, the observed cross section times branching fraction is 1.28
$^{+0.18}_{-0.17}$ times the standard model prediction for the Higgs boson with
a mass of 125.09 GeV. This is the first observation of the Higgs boson decay to
W boson pairs by the CMS experiment.
