Distinguish weather, the atmosphere's condition at a specific time and place, from climate, the long-term average pattern for a region, and interpret climate data.
Weather is what the atmosphere is doing right now, or over the next few days, in one specific place: today's temperature, this afternoon's rain, this week's wind. Climate is the long-term average pattern of weather in a region, usually described using at least thirty years of data, including typical high and low temperatures and typical rainfall for each month of the year.
The two ideas are easy to mix up because they use the same words, temperature, rain, wind, but they answer different questions. "It is unusually cold today" is a weather statement about one day. "Our region has mild, wet winters and warm, dry summers" is a climate statement built from years of averaged data. A single cold day does not change a region's climate any more than one tall friend changes the average height of your whole class.
Mastery looks like: They can correctly sort real statements into weather or climate and can read a climate data table to summarize a region's typical pattern.
Common stumbles: Using one day's unusual weather as evidence about climate; confusing "average" with "exact" when reading a climate table.