Using a novel no-arbitrage model and extensive second-moment data, we decompose conditional volatility of U.S. Treasury yields into volatilities of short-rate expectations and term premia. Short-rate expectations become more volatile than premia before recessions and during asset market distress. Correlation between shocks to premia and shocks to short-rate expectations is close to zero on average and varies with the monetary policy stance. While Treasuries are nearly unexposed to variance shocks, investors pay a premium for hedging variance risk with derivatives. We illustrate the dynamics of the yield volatility components during and after the financial crisis.