(closest channel I could find) Rumor has it that when the Fed meets this week, they'll be lowering interest rates. But if they do, how long does it take for that to impact mortgage rates? I'm specifically looking to refinance, and while I'm not trying to time the rates, I'm willing to wait days or low number of weeks if it helps

The speculation is already incorporated into the rate.

But what about when the facts are actually published? Surely that would impact rates, no?

Thanks for the fascinating question—just spent the past 10 minutes looking up some literature on this. Found a well-cited paper (Hamilton, 2008) that concludes:

The current mortgage rate reflects a rational anticipation of all future Fed policy actions. In order to change the mortgage rate, the Fed must do something other than what the market anticipated, and any change in Fed policy shows up in mortgage rates as soon as the market anticipates it.

I.e., what @flaky-twilight-96983 said. Disclaimer: I did not read the paper itself, but the conclusion makes logical sense. Same relationship between stock prices and companies. Hamilton, J. D. (2008). Daily monetary policy shocks and new home sales. Journal of Monetary Economics, _55_(7), 1171-1190.

Hmmm so operating off of that, the rates currently reflect that the Fed will lower rates. So if they lower rates, mtg rates stay the same. If the Fed raises rates (unexpected) then mtg rates go up, and if the Fed lowers rates even more than anticipated (which I personally think is unlikely), only then to mtg rates go down. By that logic, my best bet is to lock in a rate before the Fed says anything.

Roughly The current rates should reflect the probability-weighted expected future rate, which is likely not a possibility itself. If the rate they change to is lower than the expected value, rates should drop, and vice versa. But the differences here may be miniscule.

Also, the fed is lowering short term rates (overnight borrowing from the fed). Mortgages are lenders guesses at the average rates they need over 15, 20, 30 or some other number of years. Thus, it is not tied that closely to what the fed does.