The January weather that left Washington-area residents reeling from some of the coldest temperatures in recent history is now delivering a follow-up blow in the form of record heating bills from public utility companies and independent fuel suppliers.

The sharpest increase in costs will be felt by consumers who heat their homes with natural gas, roughly 53 percent of the Washington area's 1.1 million households. The average natural gas consumer will pay $172 for heating last month, a 45 percent increase over the previous January's $119.

Washington Gas Light Co. officials said that about half of the increase is due to the abnormal cold weather and the rest to rising costs from decontrol of natural gas at the wellhead and from rate increases granted by local regulatory boards.

"Mother Nature hit our customers with a one-two punch -- low temperatures and high bills," said Paul Young, a spokesman for the utility. As a result, he said, "This will be the highest bill that many of our customers have ever received."

Actual bills will vary widely, however, depending on individual customer use and conservation efforts. The billing cycle also can make a difference, since some cold January days may be included on a bill with milder December or February days.

During a normal January, a residential customer uses about 240 therms, Young said. In January 1981 the weather was 11 percent colder than normal, resulting in an average customer use of about 265 therms. This year the weather was 29 percent colder, and the average use increased to 316 therms.

Homeowners who rely on heating oil -- and about 31 percent of area households do -- also paid more to stay warm last month.

Although there is no central point for information about heating oil costs, a random sampling of area firms that sell and deliver fuel to customers indicated that business volume and prices were up significantly from last January.

The District of Columbia homeowner who spent $150 on heating oil in January 1981 probably would have paid $185 for oil this year -- a 23 percent increase in cost -- according to Ralph Moore, president of Hessick Fuel Oil Co. Customers who have larger houses or who live in the suburbs probably would have even larger cost increases, Moore said.

George Mockabee, who operates his own fuel oil business in the Maryland suburbs, said he sold about 10 percent more oil last month than he did in January 1981. The cost for some customers, he said, doubled from about $150 for a normal January to about $300 this year.

The increase in heating oil bills reflects the additional fuel burned by residents as well as the higher price for the heating oil, suppliers said. A gallon of heating oil now retails for about $1.26, about 6 cents more than last year, they said.

Electricity, which provides the main source of heat for about 10 percent of Washington-area homes, cost consumers about 12 percent more this January than last year. And the average increase would have been even more if customers had not curbed their consumption.

Potomac Electric Power Co. customers who have all-electric homes paid an average of $174.45 for 2,812 kilowatt hours of electricity last month, compared to $156.24 for 3,282 kilowatt hours in January 1981.

Higher costs for coal and oil as well as Pepco rate increases pushed up the prices, according to spokesman Nancy Moses.

Both Pepco and WGL delivered record amounts of power to customers during the month of January. The electric utility hit a new winter peak of 3,091 megawatts on Jan. 11, compared to the previous winter peak of 2,861 megawatts in 1981. That is well within the Pepco system's capability of 5,000 megawatts.

WGL sold 211.1 million therms of natural gas this January -- up 15.6 million therms over last January. Revenues for sales last month are expected to total $114.4 million. That is roughly one-fifth of the revenues for an entire year.

"January is the key usage month" for a natural gas utility company, according to Young.

It also is a key month for consumers struggling to pay higher heating bills. Young said that consumers who can't pay their utility bills should call the company immediately at 750-1000.

WGL may refer the customer to one of the agencies established in the various jurisdictions to help eligible consumers with their energy bills, Young said. Another option, he said, is to work out a payment program with the customer.