Central America's hot spots are likely this summer to get even hotter. This is the assessment of a number of Reagan administration specialists as they analyze:
* An Army offensive and proposals for elections in El Salvador.
* Reports of new East-bloc arms shipments to leftist-led Nicaragua.
* Plans by CIA-backed guerrillas to drive deeper into Nicaragua.
On the peace front, Richard Stone, President Reagan's special envoy to the region, left Washington for El Salvador on Thursday. Beyond describing it as a ''delicate diplomatic mission,'' officials will not say much about Ambassador Stone's second trip to the region. But the envoy apparently hopes to facilitate talks on the subject of elections between El Salvador's government-appointed peace commission and Salvadorean guerrilla representatives.
Stone, a former United States senator, has leaned in favor of the idea of talking directly with guerrilla representatives. But the guerrillas' political front has denounced plans for new elections in El Salvador as a farce.
For Stone, the delicate part of all this comes in trying to assure the Salvadorean government that in dealing with the guerrillas, he will not be undermining the government. Salvadorean government officials and Army officers have complained recently that their morale is being harmed by American criticisms and by what they term heavy-handed attempts to influence their conduct.
Reagan administration officials doubt that Stone can produce immediate results. Some suggest that his main usefulness at this point is in relieving the pressure from US congressmen who want to see a negotiated settlement of the Salvadorean war. What the analysts in the administration are watching most closely is the situation on the ground, where all sides seem to be preparing for more fighting.
''Never mind the hot summer,'' said a State Department official. ''I think we're in for a fairly hot year or two.''
Among the ''optimists'' in the administration, some officials and military men say they are convinced that if current levels of aid to the Salvadorean government are maintained, the government can win the war within two to three years. Other officials argue that higher levels of aid will be required.
The optimists' view was made public at the end of June by Col. John D. Waghelstein, the departing commander of the 55 American military advisers in El Salvador. At a news conference and in a series of interviews, Colonel Waghelstein, an expert on counterinsurgency, declared that the Salvadorean army could win the war in two years if the aid and planned expansion of the Salvadorean armed forces continue.
In an interview with United Press International (UPI) released on Thursday, Waghelstein predicted an increase in the fighting right through the Salvadorean presidential elections, which have been tentatively planned for November or December. (Some officials say that for a variety of reasons, the elections may be postponed until early next year).
Waghelstein said from January through mid-June the Salvadorean Army had lost 480 men killed in action plus about twice that number wounded.
''It's high and it's going to get higher,'' the colonel said of the casualty rate. ''But there's no way to beat the guerrillas by sitting. You are going to have to go look for them.''
The Salvadorean Army recently launched a 4,000-man offensive into two key cotton-growing provinces, San Vicente and Usulutan, in what is widely regarded as a major test of El Salvador's new high command. Defense Department specialists argue that the quality of the Salvadorean officer corps is improving.
But officials also say the guerrillas' campaign to sabotage the economy has been devastating. Because of increased fighting, cotton farmers have drastically cut the amount of land they are planting. One aim of the new Army offensive is to reopen farms, schools, and government services.
In his farewell interview with UPI, Waghelstein argued that along with the fighting, it was essential for the Salvadorean government to continue with its agrarian reform program, now under attack by a number of conservatives holding positions in the government and national assembly. The colonel said the war could not be won without reforms that address the root causes of the insurgency and ''steal the thunder from the guerrillas.''
In nearby Nicaragua, meanwhile, more fighting is expected, and soon. Leaders of the CIA-backed, anti-Sandinista forces based in Honduras have let it be known that they plan to start within a matter of weeks a major new offensive, thrusting deeper into Nicaragua. In the Nicaraguan capital of Managua, some sources say they expect intensified attacks to come around July 19, when the leftist regime celebrates the fourth anniversary of the victory against the late President Anastasio Somoza.
The CIA-supported ''counterrevolutionaries,'' as they are called by the Sandinistas, so far have been unable to cause much damage to Nicaragua's leftist regime beyond a relatively narrow strip of territory along the northern border with Honduras. They have tried unsuccessfully on several occasions to take the town of Jalapa, near the border.
But the leaders of the Nicaraguan rebel forces claim in recent months to have recruited new men who can be thrown into a more powerful offensive. One aim of the rebels seems to be to convince members of the US Congress that they are an effective force and thus worth being given continued aid. The Reagan administration is currently trying to find a compromise formula that would avert a House of Representatives vote to cut off aid to the Nicaraguan guerrillas.
The State Department issued a statement Tuesday contending that Nicaragua is bolstering its defenses. The statement said deliveries to Nicaragua of Soviet and other East-bloc-supplied arms were running at a rate higher than in 1982. It said the new equipment included rocket launchers, armored personnel carriers and helicopters, as well as trucks and field kitchens.