Are All Industries, "Seasonal"?

Ok, this is a weird question.

We know for a fact, that certain types of markets perform best during the summer, or winter, or around specific Holidays.

But I've always wondered if there are more subtle, seasonal factors that impact ALL INDUSTRIES.

Say for instance, an industry like home improvement. Its seasons might be spring to early summer, and fall to early winter. People wanna get their homes in shape for the Holidays, then people want to get their homes in shape for summertime.

But what about other industries? Like HUGE companies like Walmart or Target.
I know they can change inventory, to suit different seasons, but if you read online "what is the worst month for sales", and you REALLY do some thorough research, you see an awful lot of people saying that August and Sept are the worst month for sales.

I think it could be a variety of reasons -

Many people are taking "late vacations". Afterall, August is the month for family vacations. Most my friends and family, always go on vacation in late august.

September is also "the month of distraction". Kids are going back to school, schedules are changing, people are busy and perhaps even SAD that the summer is over. I know that some people like winter time. But there is no such thing as "fall fever". If you ask me, "spring fever" exists for a reason. The country thaws out, people become motivated, they smell the spring air, so they're ready to spend money.

The reason I'm asking is I noticed that business was BOOMING between april to july. But by the 2nd week of August traffic has been cut in half. To make things more ironic, my rankings are BETTER now, then they were the last few months. So I was expecting an increase in traffic and sales. And even now, in late September, business is still really slow.

So I started reading online, and I see A LOT of people saying that August is the worst month for business and sales, and that September isn't much better, with the exception of a few select industries (clothes stores and what not).

But I'd like to see what other warriors think about this. I know my industries are seasonal. And this happens every year, which is why I PLANNED for it this year. I got dozens more keywords ranking, spent some good money on PPC, did some direct mail ads.... and with all of this extra shit I'm doing, I'm still nowhere near where I was between april - july. I was barely doing any marketing at all (other than maintaining rankings), and business was on fire.

So I'm curious... how have your sales been in August in September?

I'm trying to get feedback from people in a variety of different industries. Like I said, I know there are specific seasonal influences that impact specific seasonal businesses. But I still think, for *most* businesses, that August and September can't be good months for sales.

Am I wrong? Or am I projecting my own seasonal businesses onto other industries? Because I read online and found dozens of people in other industries, saying the same thing. August and September usually suck for business.

What do you guys think?

-Redshifted