Historical weather data, all-time temperature records, and monthly climate averages for Mason City, IA. Explore typical weather conditions by week for trip planning, and see how today compares to the historical record.
April 4 in Mason City runs cool, with an average high of just 51° and a low of 30° across 127 years of records. The date has seen wild swings though — a balmy 81° back in 1929, and a brutal 8° low as recently as 2018. There's a 30% chance of precipitation today, with a small but real 6% shot at snow.
Mason City plays no games when it comes to extremes — the thermometer has hit 107° in July and cratered to -45° in February, a 152-degree spread that tells you everything about Iowa's climate personality. A single June day in 1900 dropped 7 inches of rain, and a March storm in 1933 buried the city under 15 inches of snow.
Summer is the sweet spot, with highs peaking around 84° the second week of July before tapering off through September. If you're cold-averse, January is brutal — average highs barely crack 25°, and the first week of the year is historically the coldest. Plan around late May if you're watching for rain, as that's Mason City's wettest stretch of the year.