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Despite a record-breaking heatwave this summer, in which daily high temperatures in Arizona, US topped a scorching 43°C (110°F) for 31 days straight, Ann Morton (Cloud Appreciation Society Member 40,732) never abandoned her morning hikes around Phoenix with the dogs. Although it may look as if they were here walking into an inferno, this was no wildfire. Falling streaks of rain ahead were being lit by the morning sun. But this rain never reached the ground. It evaporated away before being able to wet the parched desert below. For this reason, the streaks are known not as precipitation but as the cloud feature virga, named from the Latin for ‘stick’, or ‘branch’. Since the formation results from falling raindrops evaporating in dry air beneath the clouds, virga is associated with low humidity. The rapid evaporation of the raindrops as they fall has the effect of cooling the air. Although the rain never touches down, the column of air it evaporated away in can be cooled rapidly enough to sink violently amid the surrounding warmth. It can plummet to the ground as a ‘dry downburst’, producing damaging winds that are a feature of the desert monsoon season. Ann was not the only one to be struck by the incandescent appearance of the virga. She remembered that ‘even the dogs were amazed – and somewhat wary.’