With cloud in the forecast for at least some parts of the US, eclipse-hunters might be bracing themselves for disappointment.
But a cloudy eclipse can still be spectacular.
Growing up in south west England, I witnessed the total eclipse of 1999 – and at our vantage point on the western edge of Dartmoor, thick clouds stubbornly blocked our view of the moon and the sun.
In spite of this it was a remarkable spectacle.
As totality approached the world darkened eerily, as if dusk was falling. It became noticeably colder and the sounds of August birdsong stopped as nature reacted just as it would at nightfall – and the awestruck crowd fell just as silent.
So if you’re fortunate enough to be in the zone of totality today don’t be too downcast if it ends up overcast. My cloudy eclipse is something I’ll remember for the rest of my life.