A stratospheric warming event over northern Russia in late FEB/early MAR caused a weather pattern that produced unusual cold and snow in Europe in March, Canada/U.S. in April and lingered northeast Canada in May. One extreme breeds another. South of the Canadian cold and snow in May the U.S. was record warm.
The drought condition across Australia worsened in May and based on trends in the subsurface equatorial central/east Pacific Ocean an El Nino is on the way likely to worsen the Australian drought the second half of 2018.
Warm and cool "blobs" of ocean temperatures southwest of the U.S. and in the northwest/northern North Atlantic are helping to drive a climate pattern producing extreme wet events AND expanding drought.