The hills, where elephants recently roamed, are now bare. Even the roots have been pulled out, leaving nothing to hold the parched soil together as rainwater washes downhill, potentially taking tents and people with it and quickly inundating low-lying settlements. The United Nations says 100,000 refugees are at acute risk from landslides and floods.

The early rains — known in Bengali as kalboishakhi, which translates loosely as the storms of an “evil summer” — are a precursor to the full-on monsoons. They strike when the soil is still dry and especially susceptible to mudslides. The only warning of their approach is usually hot winds that send the dry earth of summer swirling through the air.

“You have whirlwinds of dust,” said Iffat Nawaz, a spokeswoman for BRAC, an international relief agency that is based in Bangladesh. “Suddenly it gets dark in middle of the day and it pours. We usually welcome that. It’s cooling. This year in the middle of the refugee crisis, it’s not something to look forward to.”