July in Saint-Germain-en-Laye is the warmest month of the year. In July, the weather in Saint-Germain-en-Laye is typically warm. Average daily high temperature in July is about 23 degrees above zero. On average, Saint-Germain-en-Laye has 14 rainy, 9 sunny, 7 partly cloudy, and 1 cloudy day in July. The rains are usually moderate.