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The working title of the film was Miguel Pro. The title card was missing from the viewed print, which was a video release entitled Guns of the Revolution. The onscreen credit for Reverend Humberto Almazn reads: "Padre Humberto as Miguel Pro." This credit is followed by a statement, illegible on the viewed print, which named the entity giving Almazn permission to perform in the film. Almazn had appeared on stage and in many films, when, in his mid-thirties, he entered the seminary of the Missionaries of the Holy Apostles. In 1966, he was ordained. A January 1972 Variety news item reported that he was the first Catholic priest to receive a special dispensation from the Vatican to act in a motion picture. According to an October 1969 Hollywood Reporter news item, Almazn donated his salary from the film to establish a hospital and clinic for lepers in Indonesia.
After the opening credits, the following statement appears: "Mexico-1917/The Revolution/This Story is Based on Fact." The real-life Mexican Miguel Pro, S.J. (1891-1927) entered the seminary in 1911. In 1914, he was forced to flee his country for Los Gatos, CA due to persecution by Mexico's then anti-Catholic regime. In 1915, he was sent to Spain and was ordained in Belgium in 1925. By the time he returned to Mexico in 1926, priests had been forced into hiding and Pro held secret ministries, often entering a premise disguised as a beggar, policeman or businessman. After Pro was falsely accused of attempting to assassinate the Mexican president, a betrayer led the police to Pro and his brother, who were executed without a trial in 1927. On September 25, 1988, Pro was beatified as a martyr.
Rain for a Dusty Summer was the first film of American company Do-Bar Productions. A September 22, 1969 Daily Variety news item reported that the film would be shot in Barcelona and Malaga. According to an October 1969 Daily Variety news item, the troupe was forced to change the location site from Alicante to Oriheula, Spain due to rain damage.
The set designer Juan Alberto is more commonly known as Juan Alberto Soler, the way he is listed in the Variety review. Although a September 1969 Daily Variety news item reported that director Arthur Lubin hoped to line up cameo appearances of well-known actors, such as Alec Guinness, Herbert Lom and Dame Edith Evans, none of those named in the news item appeared in the film. An undated cast list found in the file on the film in the AMPAS Library adds Gustavo Re to the cast in the role of "Reales." An October 1969 Hollywood Reporter news item reported that the film was shot with a budget of under $1,000,000.