Undated (AP) _ A spate of showers has brought short-term relief to some of the nation's scorched crops, but farmers fear the return of ''blowtorch'' heat will blast what is left in their fields before the fall harvest.

And the drought may threaten next year's crops as well, experts say.

Scattered rainfall helped some fields, came too late to reverse drought damage in others and missed parts of the Farm Belt entirely. Following the showers, glaring, cloudless skies and temperatures near 100 degrees have returned.

''I'd say we're in a real blowtorch pressure-cooker right now,'' said Indiana farmer Dan Donathen, who has 300 acres of corn and soybeans in St. Joseph County.

''We've never had temperatures like this that I can recall. I'd say we're going downhill real quick if it stays hot.''

Scorching temperatures toppled records in Wisconsin, Minnesota, Michigan and Illinois Tuesday. La Crosse, Wis., set a record for the date of 102 degrees and tied a record set in 1955 with its 35th day of 90 degree or hotter weather this summer. In Minnesota, the Twin Cities set a mark with 99 degrees.

Chicago hit 100, the seventh time this year the mercury has soared into triple-digits, a new record.

Up to 5 inches of rain fell recently on central Illinois fields farmed by Larry Dallas and his brother in Douglas County, but they need more after a hot, dry spring and early summer.

''What corn there is, the rain helped, and we've got some decent-sized ears,'' said Dallas, who expects no more than half a normal harvest.

''The soybeans perked up and grew a foot, but it gets hot and dry again, we'll lose all we've gained,'' he said.

''Certainly, the drought is not over,'' said Ken Kunkel, director of the Midwestern Climate Center at Champaign, Ill.

''Soil moisture reserves are very limited and it will be difficult to fill those kernels and pods.''

Rain soaked many fields in Indiana, Ohio, Kentucky and southern Illinois in recent weeks, Kunkel said. But Iowa, western Illinois, southern Minnesota and Wisconsin got little relief.

The drought could threaten next year's crop production because it has taken so much deep, reserve moisture out of the soil.

Experts say it is unlikely that hard-hit areas will get enough rain this year to replenish the supply. That will make winter snow and early spring rains critical.

''It's going to be tough to go into the spring with adequate soil moisture,'' said Dallas, who has 560 acres in corn and soybeans.

For now, some farmers are assessing the benefit of the late-July rains.

''It's looking a whole lot better,'' said Kentucky farmer Homer Hurst Jr. of Fleming County. ''We actually cut some hay yesterday. ... We reseeded 65 acres of corn and we're hoping for a late fall. A half inch of rain a week would be a lifesaver.''

Showers made a difference in Arkansas, too.

''Sorghum was heading out - the rain made their crop,'' said Lonoke County extension agent Blair Griffin. ''The soybeans were just beginning to bloom. If it had continued to be dry, they would have lost a large percentage of their crop.''

Farmers in other states have not been as fortunate.

''It's the same old story: we need rain - we're not getting any,'' said Herb Halvorson, assistant agriculture commissioner in Minnesota, who indicated heat now may be causing more damage than drought.

''The impact on the corn and the soybeans and the canning crops has been devastating.''

In South Dakota, experts said rains came too late to save most crops. The state approved a program to provide money to help farmers and ranchers replace water supplies dried up by the drought.

Rain in parts of North Dakota also will have limited benefit, experts said.

''It's too late for most of it - all the small grains,'' said Morton County extension agent Jack Stewart. ''But there are some corn and sunflowers that are going to benefit from this rain.''

Despite some showers in July, farmers in Barron County, Wis., have given up hope for a second hay crop and a corn harvest, said agriculture agent Don Droft.

''They're green chopping (corn) for silage,'' he said. ''They've given up hope of getting any corn.''

Dallas, the central Illinois farmer, said one alternative is to sell some 1989 corn while futures prices are high, hoping to raise that much grain next year.

''After seeing a year like this, it kind of freaks you out,'' he said. ''But if we could lock in $3 (per bushel) corn for the fall of '89, that would be good.''