A new M&A boom? Not so fast.

FORTUNE -- August is usually filled with the dog days of summer, but this year corporate dealmakers skipped their vacations and went shopping instead.

Last month was the busiest August on record for global M&A volume and the $286 billion worth of deals announced marked the highest monthly level since July 2008, according to Dealogic. The activity was driven by BHP Billiton's (BHP) unsolicited $43.4 billion bid for Potash (POT), the largest takeover attempt announced this year. It was bolstered by Intel's $7.7 billion bid for McAfee (MFE). And Sanofi-Aventis' (SNY) $18.5 billion offer for Genzyme (GENZ, Fortune 500) on August 29 raised the total value of global hostile bids to date to $133.8 billion, a 26.6% increase over the previous year. Even private equity is staging a mini-comeback, with buyout interest in companies from Burger King (BKC) to Saks (SKS).

Global M&A volume is at $1.8 trillion so far in 2010, up 24% from the previous year during the same time. The value of deals in Europe and Asia rose this year, but the number of deals in each region was unchanged. The U.S. came in as the unlikely bright spot amid a fragile economic recovery. The value of M&A deals here increased only 5%, but unlike other regions, the number of deals was up 42%.

Periods of record M&A activity often signal a sign of strength in the market, with the theory being that corporate pocketbooks open up when the outlook is strong. While that may be the case during some boom times, it's important to note that exactly the opposite is true other times, notes SmartMoney's James Stewart this week in The Myth of M&A.

In 2007, when deals reached an all-time record of $4.3 trillion, the Dow Jones Industrial Average hit its all-time high. Conversely, M&A slows when the market hits new lows. Stewart notes this happened when deal activity bottomed to its lowest level since 1995 (when Dealogic started tracking M&A volume) around the time Lehman Brothers fell under in 2008 and stock prices plunged. When stocks were dirt-cheap during most of 2009, investment bankers maintained a very low profile.

M&A not always a sign of cheap stocks

Stewart notes that this pattern, while it happens for some obvious reasons, runs against the principle lesson of investing: Buy low, not high. Corporate dealmakers, it seems, have no more insight into the direction of the market than the rest of us do.

So what does this mean for the latest surge in M&A activity? Are we to believe that the mood has changed and the outlook from the corner office is bright, or will this be another replay of poorly timed deals ahead of a market slump?

It's worth pointing out that the best August ever for global M&A activity came during the worst August for stocks since 2001. The Dow Jones Industrial Average's 4.3% drop for the month was the worst since May, and the index's first down August in five years on expectations of weaker-than-anticipated growth following a series of weak economic data.

Some market pundits feared that was a sign of a new market direction, and another sign of a looming double-dip recession. But stocks abruptly changed course and greeted September warmly with a 255-point gain in the Dow yesterday.

M&A activity shouldn't be an arbiter for the market's direction, and the latest round of deals won't necessarily beget more deals. Even some of the big banks that receive huge fees for helping put together deals remain cautious.

So far, Goldman Sachs (GS, Fortune 500) leads global, US and European M&A advisor rankings for 2010, according to Dealogic. The bank advised on the five biggest global deals in August, including the Intel-McAfee deal in the U.S. and the $9.5 billion Vedanta Resources-Cairn deal in India.

JPMorgan (JPM, Fortune 500) ranked second, helping advise the BHP Billiton-Potash deal in Canada, the $21.5 billion International Power-GDF Suez deal in the United Kingdom, the $18.5 billion Sanofi-Aventis-Genzyme deal in the U.S., according to Dealogic. Credit Suisse ranked third.

Provided the deals close -- which remains questionable for some -- the big banks will see huge windfalls from the flurry of M&A activity. But the continued gloominess reflected in the broader economy may be a sign that the good times just might not last.

In a report last month on Bank of America Merrill Lynch, JPMorgan analyst Guy Moszkowski wrote that the M&A pipeline for the bank continues to grow, but management but remained cautious "as it's merely a 'pipeline,' and has yet to translate into higher completions or fees."

He added that signs are encouraging. And while this economy should welcome any signs of encouragement, a few big August acquisitions may not be enough to stage the kind of comeback dealmakers are counting on.