It used to be that only farmers and commodities traders worried about the weather. But this is changing.

At the end of January, companies will start to report earnings for the fourth quarter of 2012, along with earnings for the entire past year. A significant factor will be the two major natural disasters that hit the US in 2012: Superstorm Sandy and the summer-long drought.

These types of natural disasters are becoming increasingly common. And each year, they seem to affect earnings across a quarter or two at quite a few companies.

Superstorm Sandy, for example, hit 12 Northeast states that account for some 23 percent of US gross domestic product. Total damages amounted to $50 billion—second only to Hurricane Katrina—with close to half covered by insurance. One would think property & casualty (P&C) insurers with large exposure to the Northeast would be devastated. Although the sector fell right around the storm, the major P&C stocks have since rebounded.

The reason? The P&C space was having a banner year before Sandy hit. During the first nine months of 2012, the industry’s pretax operating income jumped to $30.6 billion, 10 times higher than the year-earlier period. In fact, as premiums firm up and East Coasters fill gaps in their coverage, Sandy is likely to be a plus for insurers.

The same positive outcome is likely for companies that help to reconstruct, refurnish and rebuild. Case in point: Leggett & Platt (NYSE: LEG), featured in this month’s “Conservative Strategy” (page 7), and Quanta Services (NYSE: PWR), which repairs and replaces damaged power lines.

On the flip side, Sandy was bad news for companies such as Hyatt Hotels Corp (NYSE: H), which had to close 25 hotels due to the storm. Verizon Communications (NYSE: VZ) and other publicly traded utilities in the Northeast will also take a hit to earnings as they invest to rebuild infrastructure.

Down on the Farm. The 2012 summer drought caused the biggest crop loss in US agricultural history, estimated at $20 billion. While most farmers’ losses were covered by a public-private crop-insurance program, upstream producers are feeling the pinch.

Profits at meat manufacturer Tyson Foods (NYSE: TSN) will be hampered by higher feed prices, while earnings at agricultural commodities producer Archer-Daniels Midland Co (NYSE: ADM) will continue to weaken.

On the plus side are companies such as Mosaic Co (NYSE: MOS), which is likely to provide more fertilizer to farmers as they increase output in 2013.