Monday: Best day for buying outerwear, like coats, jackets. Average discount is 42 percent. Also a great day to buy purses and handbags, which average 40 percent off.
Tuesday: Find the lowest prices on swimwear. Average discount is 46 percent.
Wednesday: Best day for buying footwear. Average discount is 43 percent.
Thursday: Find lowest prices on women's dress shirts. Average discount is 55 percent on Thursdays.
Friday: Get the best deals on casual shirts, like T's and tanks. They average 42 percent off.
Saturday: Another day to buy casual shirts (42% off on average) and handbags (40% off on average).
Sunday: Dresses (43% off on average) and dress pants (55% off on average) saw their lowest prices on Sunday.
Some additional savings advice as you shop online:
1. Aim for Free Shipping
Buying a dress online - even if it is on Sunday, when sales are steepest - may not be worth it if shipping costs are involved. For me, shipping can be a total deal-breaker. While you're paying extra for the convenience of not having to leave your home, an online deal easily loses its luster when shipping costs run high. Many sites - from Nordstrom to J.Crew - offer free shipping when you spend a minimum amount, usually over $100 or $200, so reserve shopping on those sites until you have enough on your list to earn the freebie. Freeshipping.org and RetailMeNot also keep a running list of online retailers offering free shipping and their codes. For example, at shoe store DSW, you can get free shipping until March 21 on orders of $35 or more by using the code SHIPR at checkout.
2. Note the Return Policy
Shop at sites that allow returns (preferably, both online and in their physical stores) - and, better yet, where you don't have to pay for shipping to return the item. Macy's, ShopBop and RevolveClothing offer prepaid shipping labels to customers who are unsatisfied with their purchase.
3. Watch the Competition
When two department stores compete - like Saks and Nordstrom - you might have extra leverage. Case in point: My mom bought my dad a winter coat from Saks.com this past Christmas. A week later she noticed that Nordstrom.com had the exact same coat for 40% off (although only in one remaining size, which was too big for my dad). Still, she called Saks' customer service and pointed them to the sale on their competitor's Web site. Sure enough, they matched Nordstrom's discount and returned 40% to my mom's credit card.
4. Wrong Size? Call Customer Service
When possible, if a certain online sale item is unavailable in your size, call customer service and ask if they can go through their database and search for the item at their physical stores. J.Crew has done this for me on a discounted bathing suit: The Web site didn't have my size in stock, but customer service found it for me at a nearby store and put it on hold for me; I picked it up the next day.
Farnoosh Torabi is a personal finance journalist and commentator. She is the author of the new book Psych Yourself Rich, Get the Mindset and Discipline You Need to Build Your Financial Life. Follow her at www.farnoosh.tv and on Twitter at @farnoosh.