METEOROLOGY

"The dandelion is an excellent barometer, one of the commonest and most reliable. It is when the blooms have seeded and are in the fluffy, feathery condition that its weather prophet facilities come to the fore. In fine weather the ball extends to the full, but when rain approaches, it shuts like an umbrella. If the weather is inclined to be showery it keeps shut all the time, only opening when the danger from the wet is past."
Camping For Boys by H.W. Gibson

Or you could just look out of the window.

It says it's sunny.