  We combine AAVSO and VSS/RASNZ optical and Extreme Ultraviolet Explorer EUV
light curves of dwarf novae in outburst to place constraints on the nature of
dwarf nova outbursts. From the observed optical-EUV time delays of 0.75-1.5
days, we show that the propagation velocity of the dwarf nova instability
heating wave is ~ 3 km/s.
