MOSCOW, SEPT. 17 -- After helping to end the Cold War, Mikhail Gorbachev and Ronald Reagan met today in the Kremlin and talked about the weather.

"It must still be warm over there in San Francisco and L.A.," Gorbachev said.

"Yes," Reagan said.

"Well," Gorbachev said, "this is kind of unusual weather in Moscow this time of the year."

"We expected that," Reagan said gnomically.

Reagan's visit to the Soviet Union, at Gorbachev's invitation, has the feel of two allies on a nostalgic journey. It's possible that for both men, the most euphoric moment of their careers was the Moscow summit of 1988. Gorbachev was enjoying the last bit of Gorbamania (he now ranks eighth among political figures in Moscow opinion polls), and Reagan, the lifelong anti-communist, had the pleasure of visiting an Evil Empire that no longer seemed so evil.

Reagan has grown visibly older in retirement, though a bit richer from extravaganzas like his $2 million speaking tour in Japan. (He came to the Kremlin, by way of the Berlin Wall, for free.) When he arrived at Gorbachev's office, the two men embraced and clutched each other by the forearms like old friends. After they ran out of weather talk, Gorbachev, a man with a distinct dislike for conversational dead spots, picked up the pace with a mini-speech for Reagan and the assembled press pool.

"Well, I'm very happy to see that the agreement that we reached about your coming here at this time, not only as a tourist but also as somebody who made a very big contribution to the development of Soviet-American relations, has finally come about. I'm sure you must have sensed by now during your stay here in the country that we and the Soviet people hold you in tremendous esteem and respect."

Reagan expressed his humility, and the press was ushered out so the two men could talk. The Reagans are on the second day of a five-day tour of the Soviet Union. On Sunday they visited various tourist sites in Leningrad, including the Hermitage Museum.

Earlier in the day, Reagan addressed the Supreme Soviet's International Affairs Committee and gave a performance that in word and gesture could only be called vintage. Speaking to a long table of committee members, Reagan began in his bedtime-story-mellow voice:

"In America, there is a folk story about a man named Rip van Winkle who lived long ago. One day, it seems, Rip van Winkle fell asleep under a tree and stayed there 20 years.

"Nowadays, if Rip van Winkle were to fall asleep in the Soviet Union, he would only have time for a short nap before finding that everything had changed! This is my first visit to Moscow since my summit meeting with President Gorbachev in May 1988, and there have been so many changes in those two years and four months that I am beginning to understand how Rip van Winkle must have felt."

Such stone-faced officials as Valentin Falin of the Communist Party leadership did not seem as if their hearts had been warmed by the fairy tale. There was no laughter, no applause. Oddly enough, the only anecdote that seemed to amuse some of the committee members was Reagan's comparison of the current nationalities crisis in the Soviet Union to the American Civil War.

As he did during his trip here in 1988, Reagan spoke in the tones of a kindly teacher, lecturing the Soviet Union politely on the basics of freedom and the economic marketplace.

"During my last visit here," Reagan said, "I met with the students of Moscow State University. I said to them that the key to progress is freedom, freedom of thought, freedom of information, freedom of communication. Under your glasnost policy those freedoms have begun to flower. But of course, having a little bit of freedom is like being a little bit pregnant -- it isn't possible. One must be entirely free to think bold -- even heretical -- thoughts and to communicate them.

"These are yeasty times, times of ferment. Freedom can bring out passions between groups of people that may boil over. When they do, cool and calm decisions are called for by leaders so as to lower temperatures all around."

Reagan described relations between the Soviet Union and the United States as one of "cautious" friendship. "We both have powerful tools of war," he said, "and neither of us wants to use them. However, we can use the knowledge about them to help blunt or head off regional conflicts or the reckless acts of renegades."

This evening, the Reagans and the Gorbachevs dined together at a dacha in Moscow's Lenin Hills.