A federal judge temporarily halted President Donald Trump’s order freezing trillions of dollars in federal grants and loans. But not before the sprawling plan had unleashed a wave of confusion — and some panic — among public and private organizations that rely on the money to fund programs aimed at everything from Meals on Wheels to solar power to cancer research.

The White House order freezing federal grants caused mass chaos and confusion across Washington, appearing to imperil government programs that fund schools, provide housing and en