July does Paris more good than harm. That is a higher bar than it sounds.

Crowds

How many other people had the same clever idea. Built from researched monthly visitor patterns, then pushed harder for public holidays, school breaks and big events.

Weather

The weather that cancels plans rather than just dampens them. Built from monthly climate baselines plus researched storm, typhoon, smoke and snow periods.

Prices

How much the dates themselves cost you. Built from researched monthly demand, with the same holiday and event surges that drive the crowds, because airlines can read a calendar too.

Comfort

Whether you will enjoy being outside or merely endure it. Built from average highs and lows, humidity and rain risk.