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Months# DaysClimateLatitudePrecipTemp°F°C
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January31Cool and Rainy500.352828-2
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February28Usual latitudes for:0.3538383RPG Weather Pattern Generator
Generate an entire year of randomized weather that's based in reality! (Assuming an Earth-like planet with similar climates.) Everything here is based off of the weather system in "Weathering the Storms" in Dragon Magazine #137.

Instructions:
If you haven't already, duplicate the original and make your own spreadsheet so you can start customizing. Change anything highlighted in yellow on this page, then click on the "Year of Weather" tab to see your weather report! It is set up to handle up to 24 months and 1000 days.

If you find a year you really like and want to save it, copy the table. Make a new sheet, then use Edit > Paste special > Paste values only. You can then copy and paste the column widths and formatting if you want to. Every alteration to the document randomizes the weather again.

This is set up for the northern hemisphere. If your setting is in the southern hemisphere and you don't want to reconfigure things, you can list the months starting with the middle of the year (e.g. July–June instead of January–December). Then you'll get summer and winter falling on the right months.
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March31Desert0–30°0.3548489
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April30Tropical Savanna0–20°0.35585814
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May31Steppes20–50°0.35686820
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June30Equatorial0–20°0.35757524
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July31Monsoon0–20°0.35757524
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August31Warm and Rainy20–50°0.35666619
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September30Warm with Dry Summer20–50°0.35575714
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October31Warm with Dry Winter20–40°0.3548489
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November30Cool and Rainy40–70°0.3539394
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December31Cool with Dry Winter50–70°0.353030-1
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Tundra70°+
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Polar70°+
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Temperature UnitsFreezing
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Fahrenheit32
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Temp outer bound:12
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Temp inner bound:4
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Chance of fog for rain:0.15
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Chance of lightning for storm:0.25
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Chance of hail for rain:0.1
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Chance of hail for storm:0.2