The next two weeks are an unusually opportune time to buy Series I Savings Bonds, both the Wall Street Journal and Savings Bond Advisor say. If you buy before May 1, you’ll earn 4.28 percent for the next six months. The rate is adjusted twice a year for inflation — and yesterdays’ Consumer Price Index report means that the next adjustment will be push the rate on these bonds to 6.06 percent. As Savings Bond Advisor points out:

These are much higher rates than are available in bank CDs or even other US Treasury securities.

Here’s why it’s important to act quickly: The I bonds’ interest rate has two parts, a fixed rate and an inflation component. The fixed rate currently is 1.2 percent, and it’s locked in for the life of the bond. New bonds sold after May 1 are likely to carry a much lower fixed rate.