Strange sandy rain

The sky was quite yellow this morning, with a queer overcast light, and I thought it was about to rain. But when it did eventually begin to drizzle, several hours later, everything that got wet was left with sandy smears over it -- my bicycle looked for all the world as if it had been through muddy water, and the blue plastic bag tied over the seat was covered in pale patches where the drips had pooled and dried. I suppose it must be another case of the sand blowing in from the Sahara again, which it does every few years...