On Monday, Tuesday and Wednesday of last week, economists all over town were telling callers there was not that much of fear from the cold. Numerous individuals were hurting, they conceded, but the overall economy or gross national product was not - at least not seriously.

By Thursday, as weather and layoff reports worsened, the economists started having doubts.

By Friday and Saturday, as a new storm struck the Midwest and East, many of them were back at their computers drawing up what one group delicately called an alternate forecast."

The basic feeling among the experts still is that the cold's effects will not be great enough to throw the economy off course.

It is true that orange juice prices are going up, they say - so most people may drink less orange juice for a while.

Factories have been closed and workers laid off - but most off the lost production and wages will probably be made up in extra hours once the plants reopen.

Family purchasing power is being drawn down by higher home-heating bills - but it will be pumped up again by the forthcoming federl tax rebate. The public as a whole will gain far more from the proposed rebate than it will lose in higher heating bills.

The trouble with these is that they are long-term calculations, and as the activist economist John Maynard Keynes once acidly observed, in the long run, we are all dead."

Another trouble is that the longer it stays cold, the longer it will take to recover. Even if the cold ends soon, the forecasters say the economy may grow a percentage point or two less in the first quarter than it would have otherwise - but they think the lost growth, and the jobs and income it represents, can be made up fairly readily in the second and third quarters.

The two most publicized effects of the cold have been factory closings in the North and Midwest and frost damage to the citrus and vegetable crops in Florida.

Most of the Florida orange crop goes into frozen orange juice, and most of the nation's frozen orange juice comes from Florida. Several days of sub-freezing temperatures move than a week ago did a still-undetermined amount of damage in the Florida orange groves; the most common estimate is that as much as 30 per cent of the crop may have been lost. That large a loss, if true, will inevitably force up prices.

But Agriculture Department economists make a number of calming points about this likely price increase, the main one of which is that frozen orange juice concentrate prices were sorely depressed before the thermometer dropped below freezing on Jan. 18.

Last year's Florida orange crop was a record 185 million boxes, and this year's was expected to be almost 20 per cent larger still - 219 million boxes. Prices had fallen accordingly, from about $2.25 for 12 six-ounce cans last summer to as low as $1.60 in early winter. Now the economists think prices might simply bounce back about to where they were.

One agricultural expert said last week he suspects at least as many growers are happy about the outcome of the last few days as are hurting because of it.

The cold also did extensive damage to Florida's winter tomato and other vegetable crops, so that tomato and other fresh vegetable prices are also likely to rise. The vegetable growers - and the migrant workers for whom they now have no jobs - are probably the clearest losers so far in the cold spell.

Private economic, forecasters like Data Resources, Inc., and Chase Econometrics think the forthcoming increase in fruit and vegetable prices will add from one to three fourths of a percentage point to this year's inflation rate as measured by the consumer price index - this year's average level of consumer prices s against last year's. But that rise in consumer index many exaggerate the real effect on consumers.

Vegetable prices are likely to staty inflated only until spring, when the next crops come in. Unless something bad happens to the spring should return toward normal.

Orange juice, meanwhile, is one of those things for which economists say demand is elastic; the higher the price, the less people buy. Agricultural economists say that in other recent times when orange juice prices have risen sharply, buying has declined, and they expect the same to happen this time. Thus the price index will rise, but people will not be paying the higher prices.

The factory closings have come about in general because of the cold and more specifically because the interstate pipeline companies have not been able to meet full industrial as well as residential demand for natural gas, and have shut some factories off. These factories in turn, for various reasons, have not been able to find alternative fuels.

Industrial users of natural gas fall into two broad catetegories. The first is made up of those that use gas as a general fuel, and could just as well use some other fuel if it were available and comparable in price. The second is made up of those that can be use only gas, because its peculiar properties make it an integral part of their production processes; an example is the textile industry, which uses gas in the finishing process because gas is smokeless and does not stain.

Most of the cutoffs have occurred in the first category, which has a low gas priority under Federal Power Commission regulations, but a few have occurred in the second category as well.

Analysts say one particularly hardhit industry has been steel, and steel production last week was 6.3 per cent below the week before. An American Iron and Steel Institute spokesman said part of the problem for some mills was that rivers had frozen and coal could not be brought in by barge. He also said the industry expects to make up the lost production later.

Textiles are another supposedly vulnerable industry, and a spokesman for the Americn Textile Manufacturers Institute said as many as 10,000 workers may have been laid off in the Southeastern states where the mills are concentrated. The 10.000 represent about 2 per cent of the textile work force, he said - and he, too, predicted the lost production will be made up once gas is restored to the cut-off companies.

No one knows at this point how many factories may have been shut down in the economy as a whole since the cold began, nor how many workers have been laid off and for how long. The government estimates 400,000 may have been laid off at one time or another, though some of these have already returned to work. Private forecasters have come up with similar estimates. Data Resources thinks lost wages will total $3 billion to $4.5 billion - but adds that this loss will be partly offset in the short run by unemployment compensation, and is likely to be offset as well by extra hours of make-up work later in the year.

Some of this unemployment effect of the cold may never show up in the official statistics. This month's official unemployment rate will be based on a survey taken the week of Jan. 9-15, before a lot of layoffs occurred, and similarly by next month's survey a lot of the layoffs may be over.

The layoff problem could become far more serious if the cold continues. So could the third major problem the cold is causing, which worries some economists even more - the extra money people are having to pay for heat, which reduces their purchasing power for all other goods and services.

There is no unemployment compensation to make up this lost income, nor any prospect like extra hours of work later in the year. Some of this money will go out of the country to foreign fuel producers, the economists say, and the rest to domestic producers, largely in the form of higher profits. In both cases most of the money is likely to leave the U.S. spending stream at least for a while. In that sense the increased heating costs act like a tax increase.

Currently, government economists estimate this increase in heating costs at $2 billion to $3 billion, which they do not regard as enough to do much damage in a $1.749 trillion economy. Economists note that a $2 billion to $3 billion heating cost increase would be offset easily by the President's proposed $11 billion tax rebate.

Let the heating bill rise a little more, however, and even the economists may be impressed.