Applying for a mortgage loan — whether it's a new loan or a refinance — sometimes feels like a big gamble.

Interest rates on the 30-year fixed-rate mortgage loan may stand at 5.1 percent today. But what if they drop to 5 percent tomorrow? Of course, they might go up to 5.3 percent, too.

Trying to guess the perfect time to refinance or lock in a mortgage interest rate is a loser's game, unfortunately. The housing market has always been a tricky one to figure. It's downright confounding these days.

The good news, though, is that the interest rates on today's mortgage-loan products are already at historic lows. If you need to take out a mortgage loan, this is the time to do it, regardless of what happens tomorrow, next week or next month.

Don't believe me? Then take a look at Bankrate.com, one of the best financial consumer Web sites out there. According to the analysts at Bankrate, the average interest rate on a 30-year fixed-rate mortgage as of this morning stood at 4.98 percent. That's an amazing rate.

And things get even better if you're interested in a 15-year fixed-rate loan. The average interest rate on these loans checked in at 4.63 percent this morning.

With rates like these — and there's no hint that they'll be shooting up anytime soon — it's little wonder that so many homeowners surfing the Internet on an hourly basis looking to see just how low mortgage interest rates can go. Problem is, this habit can lead to inertia. Homeowners who can already qualify for perfectly low mortgage interest rates are waiting for the rates to go down even lower. There is the possibility that homeowners might wait too long and see rates rise instead.

Remember, too, that refinancing a mortgage loan typically isn't free. Borrowers can expect to pay anywhere from $2,500 to $5,000 in closing costs.

Borrowers should also remember that a lower interest rate may not always bring as much savings as they hope. A homeowner with a $200,000 30-year fixed-rate mortgage loan with a 6.5 percent interest rate would have a monthly mortgage payment of $1,264.14. If that same homeowner dropped the interest rate to 5.5 percent, the monthly payment would drop to $1,135.58. That's a monthly savings of just $128.56. Borrowers will have to decide if such savings are worth the hassle of digging up past pay stubs, tax records and other sometimes-hard-to-find documents.

So if the mortgage interest rates look good to you today, maybe you should begin the refinance process. Remember, no one really knows what interest rates tomorrow — or next month — will bring.