The holidays are usually a down time for real estate action; it's tough for Realtors to show your unit to prospective buyers when you've got aunts, uncles and cousins stowed in every corner, and it's hard to find time to look at places when you're cooking your fifth batch of cookies. Which is why it's surprising to see how much rents have spiked nationally compared with this time last year.

According to the latest national rent report from real estate firm Zumper, one-bedroom rental rates are up nearly 10 percent when compared with the same time period from last year. By Zumper's calculation, the average U.S. rent for a one-bedroom will run you $1,255. That's an increase of just over 2 percent since last month. Two-bedroom units are up to $1,388. Analysts at the firm say the year-over-year growth suggests an unusual increase in demand for this time of year.

Locally, Philadelphia is still number 15 on the most expensive rentals list, and one-bedrooms are up 3.7 percent over last year. But when compared with last month's figures, the outlook improves a bit. Month over month, one-bedroom rates remained flat. Even more surprising: two-bedroom units fell just over 3 percent since last month. In Philadelphia, analysts calculate the median monthly rent for a one-bedroom to be $1,410 and a two-bedroom to be $1,550.