Thunderstorms, a cloud cover and a dust formation all were reported on the civilian weather network before the Iranian hostage rescue mission was launched, government meteorologists said yesterday.

They also said the huge dust or sandstorm that helicopters tried to buck through, one unsuccessfully, might have been detected if the civilian weather satellite had passed over Iran later on the day of launch, April 24.

But the civilian satellite with the equipment that might have detected the dust storm, which the Pentagon said rose as high as 5,000 feet and was 190 nautical miles long, passed over Iran about 7 a.m. Iran time.

Frank J. Smigielski, analyst for the U.S. government's National Environmental Satellite Service, said yesterday that the NOAA 6 satellite carries scanning gear that catches light reflected from such phenomena as a big duststorm.

"It is conceivable we would have seen it," said Smigielski when asked if the storm would have shown up had NOAA 6 passed over it around noon April 24, when the light was better.

He and other civilian weather specialists said that they presume the military's secret weather satellites have similar detection equipment which was functioning before and during the rescue mission.

A Pentagon spokesman said yesterday that "we had continuous and immediate coverage" over the route the helicopters flew from the aircraft carrier Nimitz in the Gulf of Oman to the refueling site near Tabas in the Iranian desert, called Desert One in the mission plan.

He added that military meterologists considered the weather acceptable for the eight helicopters ordered to fly low over the desert and mountains in the 500-mile trip to a site called Desert One.

All eight helicopters ran into the fierce sand or dust storm. Two of them landed on the desert for awhile to let the worst of the storm pass over, while the fifth helicopter launched from the Nimitz returned to the ship after its crew became disoriented in the storm.

As it turned out, the helicopter that turned back could have made a historic difference in the rescue attempt. Commanders found themselves down to five operable helicopters at Desert One when the plan called for at least six. They aborted the mission for lack of this sixth chopper.

If there had been six helicopters, the plan called for flying 90 commandos to a mountain hideway east of Tehran that same night, lying low during the next day and storming the U.S. Embassy the night of April 25.

Thomas B. Ross, assistant secretary of defense for public affairs, said earlier this week that the "dust or sandstorm encountered by the helicopters was not predicted because these phenomena rise rather quickly and they are not predictable except from the ground."

Iran feeds reports on its weather from ground observers into the world network. The United States and other nations receive the reports within hours by teletype.

Harlan Saylor, director of the government's National Meteorological Center, said yesterday that an Iranian weather observer near the southern coastal city of Bandar Abbas did report a dust formation at 3:30 p.m. April 24, Iranian time. The Nimitz helicopters were launched at dusk that day.

Saylor said the one dust report would not be enough to aid meteorologists planning the rescue. The big problem in predicting conditions along the helicopters' route is the scarcity of Iranian weather stations in the back country desert, he added.

Other government forecasters, when asked yesterday to analyze the civilian satellite photos of the weather over Iran for April 23 through 25, said it looked as if a cold front was swirling southeastward from the Caspian Sea to the Iranian back country.

"Definitely some activity there," said one forecaster in studying the photos of the thick arc of white clouds punctuated by spots he said were thunderstorms.

The cold air from the front would kick up quite a lot of wind as it moved along, the meteorologists said, possibly sending sand and dust high into the air.

The stressed that they did not have enough information, however, to judge whether the weather was unfavorable for the mission.

An Iranian air force general scoffed at such scientific caution, stating that "any lieutenant in our air force knows that April is a bad month for sandstorms." He said March would have been a much safer month from a flying standpoint.

The Joint Chiefs of Staff, who planned the rescue mission, said in a report sent to the House Armed Services Committee that the weather looked favorable before launch.

"All weather conditions occurred as forecasted," said the chiefs, "with the exception of the dust phenomenon. There is nothing in any of the weather data to indicate that the dust was forcastable or, for that matter, any environmental conditions that could have caused them."