During summertime, hot, muggy air masses from the Gulf of Mexico drift northward into Missouri, dominating the weather patterns. Daytime highs during the hottest months, July and August, average between 87 and 90 statewide. Luckily, cold fronts originating in Canada sometimes make their way through, particularly in the northwest, provides brief respites from the otherwise sultry, steamy atmosphere. Precipitation in summer varies.