Temperatures and humidity
We expect temperatures on Thursday to climb from the 70s early in the morning to the upper 80s by midday. Afternoon high temperatures, between 2 and 5 p.m., should generally be in the low 90s.
During the evening, temperatures slowly fall back into the 80s, before easing into the muggy 70s between sunset and around 10 p.m. (downtown).
Humidity levels are oppressive, with dew points in the low-to-mid 70s. The combination of heat and humidity, make peak afternoon temperatures feel several degrees hotter, possibly up to 100 degrees.
If you’re spending time outside, be sure to stay hydrated and find a cool place if you’re feeling overheated.
Storms may pop up randomly as early as the mid-afternoon as the sun heats the air and a weak zone of low pressure approaches. These hit-or-miss storms could become most numerous in the evening.
In general, storm coverage and intensity should start trending downward after 8 or 9 p.m. though some may linger after dark — potentially interfering with fireworks displays.
Especially during the late afternoon and early evening, any storms that develop could contain dangerous lightning, very heavy rain and strong winds.
The chance of any location getting hit by a storm is around 40 percent, so plenty of areas should end up rain-free without disruption. But pinpointing the exact timing, location and coverage of storms won’t be possible until they begin forming Thursday.
With the risk of storms and so many people outside, it’s important to remember “when thunder roars, go indoors” to stay safe and avoid any lightning injuries.
July 4 weather history
The average high in Washington on July 4 is 88 degrees, with an average low of 71. Temperatures have hit the 90s in 36 percent of years since records began in 1871.
The highest temperature ever recorded on July 3 was 100 in 1919 and the coolest 52 in 1933. Just three years ago (in 2016), Washington posted its fourth coolest July 4 on record with a high of just 74 degrees.
Measurable rainfall has occurred in four of the past five years, but that’s an unusually damp stretch. Since 1871, rain has fallen in just 36 percent of years. The wettest July 4 on record occurred in 2004, when 2.18 inches fell.