Temperature Blanket Planner
Estimate how many days will land in each of your color ranges over a year, and how much yarn of each color to have on hand before you start.
Year
Typical monthly average temperatures (°F)
This site doesn't fetch live weather data for a location — every calculator here runs entirely in your browser with nothing sent to a server, and a location lookup would break that. Look up your area's monthly averages from a climate almanac, or use last year's actual local averages as a stand-in.
Color ranges
Why this uses monthly averages instead of a daily forecast
Nobody has next December's actual daily temperatures in January, so any temperature blanket planned in advance has to work from typical averages rather than a real forecast — this tool estimates how many days will likely fall into each color band by treating each month's daily temperatures as spread evenly across a range centered on that month's average (the "day-to-day swing" field controls how wide that range is). It's a planning estimate, not a prediction: the actual blanket you crochet day by day will follow real temperatures as the year happens, and will differ from this estimate by however much that year runs warmer, cooler, or more variable than its typical average.
Getting good monthly numbers
National weather services publish "climate normal" tables of 30-year monthly average highs and lows for most locations, which are a solid input here. If your area had an unusually mild or harsh year recently, using that single year's averages instead of the longer-term normal will skew your color estimate toward that year's specific weather rather than a typical one — the longer-term climate normal is usually the better planning input.
Buying yarn for the rare colors
Whatever color range represents the most extreme temperatures for your climate — the hottest band in a mild climate, or the coldest in a warm one — will usually need only a small amount of yarn, sometimes just a partial skein. Rather than buying a full skein you'll barely dent, this is a good spot to raid the stash for a coordinating scrap, since a handful of rows in an unusual color reads as a design feature on a temperature blanket rather than a mismatch.