Today marks a complete week of 30-year fixed mortgage rate decreases. According to Zillow, the average 30-year rate is currently 6.55%, which is down three basis points since yesterday and 19 basis points since this time last week.Trump could enact his plan to impose tariffs on Canada, China, and Mexico this weekend, which could have various effects on the U.S. economy — including increasing mortgage rates. With relatively low 30-year rates today, it could be a good time to lock in an interest rate.Have questions about buying, owning, or selling a house? Submit your question to Yahoo’s panel of Realtors using this Google form. Here are the current mortgage rates, according to the latest Zillow data: 30-year fixed: 6.55% 20-year fixed: 6.40% 15-year fixed: 5.88% 5/1 ARM: 6.84% 7/1 ARM: 7.09% 30-year VA: 5.99% 15-year VA: 5.40% 5/1 VA: 6.06% Remember, these are the national averages and rounded to the nearest hundredth.Learn more: 5 strategies for getting the lowest mortgage ratesThese are today’s mortgage refinance rates, according to the latest Zillow data: 30-year fixed: 6.59% 20-year fixed: 6.34% 15-year fixed: 5.89% 5/1 ARM: 7.02% 7/1 ARM: 6.81% 30-year VA: 5.95% 15-year VA: 5.59% 5/1 VA: 6.08% 30-year FHA: 6.49% 15-year FHA: 5.88% Again, the numbers provided are national averages rounded to the nearest hundredth. Mortgage refinance rates are often higher than rates when you buy a house, although that’s not always the case. Use Yahoo Finance’s free mortgage calculator to see how various interest rates and term lengths will impact your monthly mortgage payment. It also shows how the home price and down payment amount play into things.Our calculator includes homeowners insurance and property taxes in your monthly payment estimate. You even have the option to enter costs for private mortgage insurance (PMI) and homeowners’ association dues if those apply to you. These details result in a more accurate monthly payment estimate than if you simply calculated your mortgage principal and interest.There are two main advantages to a 30-year fixed mortgage: Your payments are lower, and your monthly payments are predictable.A 30-year fixed-rate mortgage has relatively low monthly payments because you’re spreading your repayment out over a longer period of time than with, say, a 15-year mortgage. Your payments are predictable because, unlike with an adjustable-rate mortgage (ARM), your rate isn’t going to change from year to year. Most years, the only things that might affect your monthly payment are any changes to your homeowners insurance or property taxes.The main disadvantage to 30-year fixed mortgage rates is mortgage interest — both in the short and long term.A 30-year fixed term comes with a higher rate than a shorter fixed term, and it’s higher than the intro rate to a 30-year ARM. The higher your rate, the higher your monthly payment. You’ll also pay much more in interest over the life of your loan due to both the hig