Free calculator · No signup
Extreme Heat Days Calculator — By ZIP Code
Enter your ZIP code, a start date, and a heat threshold to count real extreme-heat days for your exact location, pulled from historical weather data.
Your numbers
Result
Enter your ZIP code and start date, then tap Calculate.
How it's calculated
Counts every day from your chosen start date through today where the daily high temperature met or exceeded your selected threshold, using real historical daily highs for your ZIP code's coordinates.
Also reports the single hottest day recorded in that window, for quick reference.
Historical weather archives typically lag ~5 days behind today, so the most recent few days may not be counted yet.
Row Wise tracks heat stress, growth stage and irrigation timing automatically for your actual field boundary all season — not just a once-off lookup.
Get notified at launch →Frequently asked questions
What threshold should I use?
95°F is a common general heat-stress marker for crops and cattle. 100°F and 105°F are useful for tracking more severe, damaging heat — pick whichever matches the risk you're watching for.
Why does this matter for crops and livestock?
Extended stretches above these thresholds are linked to pollination failure, reduced fiber/grain fill, and heat stress in cattle. Counting actual extreme-heat days for your location gives a concrete number instead of a general impression of "a hot summer."
Why might today's temperature be missing?
Historical weather archives are usually a few days behind real time. If the last day or two looks low, that's likely because the archive hasn't caught up yet, not a data error.