Even though there's less than a dozen companies that still report monthly retail sales, those that did report April numbers disappointed and confirmed that the spring season is off to a slow start.

L Brands, the maker of Victoria Secret, was especially disappointing—sales at the flagship Victoria Secret brand were down 1 percent, well below expectations of a gain of 4 percent.

But they weren't the only disappointments...Costco, Zumiez, Buckle and Cato were all below expectations.

What happened? First there's the weather, which this time really has been disappointing—and it's been poor into May. It's been cloudy in New York for a week and a half. I just spoke to an analyst in Atlanta: it's supposed to be 75 degrees, it's 51 and cloudy.

This is in contrast to February and early March, when the weather was fairer and warmer. It's likely some demand was pulled forward.

One thing's for sure: there seems to have been a pickup in promotional activity and clearance markdowns in the second half of April. Wedbush noted this trend on Monday and cut estimates for a number of apparel stores, including Chico's, Express, and Gap, which reports April sales Thursday.

There's also been some discussion on deflation, particularly in food. Susquehanna had a note out Thursday morning saying that athletic shoe prices have been declining for two years but that this has been offset by unit gains.

Then there is the continuing impact of the Amazon juggernaut, which owns the Zappos shoe site and the 6pm.com discount site, as well as its usual portal. One analyst estimated that Amazon will likely sell more than $10 billion in retail this year.

The effort to sell online has been slow and difficult. Some retailers like Williams-Sonoma get roughly 50 percent of sales online, but they are the exception: for most it's 10 to 15 percent.

There's another problem: for most retailers, the move to online is less profitable than store profits, due largely to shipping costs. Once you have the store, if you sell one less item, you are deleveraging the store. Of course, if you are getting new sales online, that would be good news. But for the most part, that's not what's happening: retailers are just cannibalizing in-store sales.

And once you are online, there is tremendous price competition, as companies like Nordstrom are discovering.

The hope now turns to Mother's Day this Sunday, at least it looks like the weather in the Northeast and Midwest is warming up. Let's hope that trend continues.