Do overcast skies mean heavy rains are on their way?

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Dear Tom,
Do overcast skies mean heavy rains are on their way?
— Faith Yotze, Mzuzu University, Republic of Malawi

Dear Faith,

An overcast sky does not mean heavy rain, or precipitation of any sort, is on its way. That is as true in Malawi as in any place on Earth. The reasons for an overcast sky are many and varied, and although an overcast sky can certainly indicate that rain is likely to occur, it is definitely not a guarantee. For example, high cirrus clouds made up of ice crystals can cover the sky simply as a result of upper-level jet stream flow/orientation. I am confident that your own personal experiences attest to that.

Malawi is a small, landlocked nation in southeast Africa. Its climate is hot in the lower-lying areas in the south of the country and temperate in the northern highlands. The altitude, generally 1,500-5,000 feet, moderates what would otherwise be an equatorial climate