Did June feel unusually hot and humid to you?

For around 240 million people across the United States, the month was at least a degree warmer than average. Only around 9 million people nationwide experienced a cooler-than-average June.

In 41 contiguous states as well as Washington, D.C., monthly temperatures were at least a degree above average. But it wasn’t the days that were most unusually warm — it was the nights. A total of 44 states and D.C. experienced above-average low temperatures, which meant less relief from the heat after sundown.

A brutal heat wave that hit much of the U.S. last week also fueled above-average dew points, a measure of humidity, across dozens of states for June — a factor that increases the risk for heat-related impacts. The combination of unusually high humidity and temperatures factored into weather that went well beyond what’s typical of summer conditions in the Northeast.

The Northeast, Mid-Atlantic, Carolinas, and Ohio and Tennessee valleys experienced the most humid conditions compared to normal for the time of year — a trend that looks to continue through July.

An unusually warm June

Near the East and West coasts, there were strong high-pressure cells that contributed to a warmer-than-average month in most places. Those high-pressure cells cause air to sink, compress and warm. They also pushed the jet stream, a dividing zone between cooler air to the north and warmer air to the south, into Canada.

More frequent winds from the south, drawing in tropical air masses from the Caribbean Sea, and warmer-than-average ocean temperatures in the Gulf of Mexico and western Atlantic also help explain why the month was unusually warm.

Low temperatures

One of the most notable aspects of the June heat dome was just how warm the nights were. Cities such as New York and Minneapolis had their earliest 80-degree overnight-low temperatures on record. In Baltimore’s Inner Harbor, an overnight low of 87 degrees broke a June record.

This led to swaths of the Midwest, Northeast and Mid-Atlantic experiencing well-above-average minimum temperatures during June — including about 85 million people nationwide.

Nighttime temperatures were also warmer than average in many western states.

With climate change, the number of hot nights is rising. For those without access to adequate cooling and hydration, warm nights can disrupt sleep patterns, which can contribute to many negative health impacts.

High temperatures

Even with the recent eastern heat dome, June high temperatures were most unusually warm in northwestern states. The states where daytime heat was most atypical include Idaho, Washington, Nevada, Oregon and Utah, where an early June heat wave boosted temperatures.

In northern Alaska, where monthly temperatures were above average, snow melt caused record flooding in the Sagavanirktok and Colville rivers, according to Alaska-based climate scientist Brian Brettschneider. This flooding washed out part of the Dalton Highway — the sole roadway connecting the state’s biggest cities to northern oil fields — prompting the declaration of a state of emergency.

More humidity than normal

June was more humid than normal for a whopping 290 million people across the country. For 110 million of those people, the month featured well-above-average humidity.

During last week’s heat dome, record-breaking dew points were observed in several states as well as southern Canada, contributing to heatindex values that exceeded a dangerous 115 degrees in some areas — highly atypical for the Northeast.

This caused record-breaking levels of thermal stress — based on a combination of temperatures, humidity, winds and solar radiation — for a densely populated stretch from New York to North Carolina.

It’s another important indication that the pattern produced more than just normal summer weather.

A hot start to July

July will begin on a hot note across the West, with heat warnings and advisories in effect for the Northwest and Southwest, and red-flag warnings for enhanced fire weather risks across Northern California.

That heat will spread into the northern Plains and Midwest late in the week, with moderate-to-major risks for heat-related impacts developing from St. Louis to Chicago and Minneapolis.

Along the East Coast, hot and humid weather early in the week will ease by midweek, but above-average temperatures are forecast to return by Sunday.

There are strong signs that July will follow in June’s footsteps as an unusually hot and humid month.