With the U.S. Federal Reserve's July monetary policy meeting a day away, expectations for an interest rate hold weakened quickly on prediction markets.

On July 27, Decrypt reported that over the past 24 hours the probability of a hold fell on prediction markets Polymarket and Myriad, while the likelihood of a 0.25 percentage point hike rose.

The biggest shift was on Polymarket. In the market, which reflects contract prices like crowd-based probabilities, the "no change" outcome fell 8.9 percentage points over the past 24 hours to 73.25%. The chance of a 25 basis point hike rose 9.7 percentage points to 26.65%. Total trading volume was $100.83 million, and volume over the past 24 hours was $5.78 million.

Myriad, run by Dastan, showed a similar trend. The market put the probability of "no change" at 74% and the probability of a hike at 27%. Over the past day, the hold side fell 9% and the rate-hike side rose 8%.

Federal funds futures, which reflect professional rate traders, also moved in the same direction. As of the afternoon of July 27, federal funds futures implied a 37.6% chance of a rate hike. As of the afternoon that day, the hike probability was presented at 38.8%, showing that markets broadly see a meaningful chance of an increase.

The scenario drawing attention this time is a 25-basis-point hike. One basis point is 0.01 percentage point. If the Fed raises rates by 25 basis points, the current target rate range of 3.50% to 3.75% would rise to 3.75% to 4.00%. If rates rise, borrowing costs go up and consumption and investment may slow, increasing pressure on risk assets such as bitcoin and technology stocks.

The backdrop is that recent inflation and the Fed's prior signals are diverging. The Fed warned in its June meeting, when it held rates, that inflation remained high. At the time, the median of Fed officials' year-end policy-rate projections was 3.8%. June inflation, however, fell to 3.5% from 4.2% in May, giving policymakers grounds not to rush.

For this reason, while markets still see a hold as the more likely outcome, they are pricing in more than before the possibility that "the Fed may make an unexpected decision." Both Polymarket and Myriad still assign a higher probability to "no change," but the key point is that probabilities were sharply repriced in just one day. Federal funds futures are also seen as a leading indicator that prices in the Fed's next move, making it hard to view the shift as a temporary move limited to prediction markets.

The Federal Open Market Committee will meet on July 28-29. The Fed is expected to announce its rate decision on July 29. Market focus is moving beyond the simple question of a hold to whether the Fed maintains the inflation-warning stance it laid out in June or continues a wait-and-see approach reflecting the recent cooling in inflation.