"Here the Pharisees and Sadducees approached him, and to test him, they asked him to display to them a sign from heaven."
"In reply he said to them: “When evening falls, you say, ‘It will be fair weather, for the sky is fire-red,’ and in the morning, ‘It will be wintry, rainy weather today, for the sky is fire-red but gloomy.’ You know how to interpret the appearance of the sky, but the signs of the times you cannot interpret."
"A wicked and adulterous generation keeps seeking a sign, but no sign will be given it except the sign of Joʹnah.” With that he went away, leaving them behind."
What "evidence" is there that the weather is changing?
If you've been alive long enough, you recognize certain patterns. The wind picks up. The humidity changes. The clouds are moving. The sky darkens or changes color. You can smell the rain on the gusts.
God's Word has always provided direction prior to a storm. There have been many "days of Jehovah" where He made an accounting or a reckoning with a person or a nation or a group. His Word has always come true.
Jesus is illustratively called "The Word" because he has always been part of relaying Jehovah's messages to humankind. The fact that Jehovah's Word has always come true is evidence that the Jesus of the Bible not only exists but has existed since the beginning of creation.
For someone to doubt his existence is madness.