Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of specialty chemical maker American Vanguard (NYSE:AVD) fell 17% today after cautioning about second-quarter earnings.

So what: Wet weather in the Midwest and Southeast will negatively affect the company's performance in the second quarter and the company doesn't expect to meet either top- or bottom-line expectations. Revenue is expected to top last year's $84.8 million but won't hit Wall Street's $106.8 million expectation.  

Now what: American Vanguard didn't give an update on what profit would look like, but investors are expecting the worst. Some of these sales will not only be delayed but will also be lost altogether, and that's the biggest concern today. But long-term this isn't a blow to the company's market share and weather won't have this kind of impact every year. The stock trades at 14.7 time trailing earnings now, and considering that revenue will still grow despite bad weather, I think this is a buying opportunity for long-term investors.

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Fool contributor Travis Hoium and The Motley Fool have no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.