The heat dome that’s holding a mass of scorching, Sahara-like heat over our heads is not only torching our daytime highs here in the Valley but also elevating our overnight lows.

And people’s tolerance for hot weather diminishes with every extra degree of night temperature. After enduring hot days, hot overnight temperatures keep those without air conditioning from getting any relief, putting further strain on their bodies and leaving them more vulnerable to heat exhaustion and heat stroke, which can be deadly.

It’s especially hard on the elderly, children, and people with chronic illnesses, said meteorologist Antoinette Serrato with the National Weather Service in Hanford.

Neighborhood Trees Lower the Temperature

But where you live determines how warm it stays at night. On Sunday night, after a forecast high of 111, the nighttime low is forecast for 81 degrees in Fresno.

And that’s at the airport. Downtown Fresno and other parts of the city where there are many buildings and few trees could feel even hotter by a couple of degrees, Serrato said.

Bakersfield, which like Fresno is a big city with a lot of concrete and comparatively fewer trees, has a forecast high of 114 on Sunday and an overnight low of 83.

The overnight lows will be 78 in Visalia, 77 in Hanford, and 76 in Reedley.

The further you are from a heat island, the better. In Madera and Merced, for example, after a daytime high of 111 Sunday the overnight low from Sunday to Monday is forecast for 75 degrees.

Cooler Nights in Rural Towns

West of Fresno in more rural areas, the overnight low from Sunday to Monday will be a comparatively mild 73 degrees in Firebaugh and Kerman and 74 degrees in Mendota.

After the worst of the heatwave passes, the overnight lows in Fresno will dip down into the 70s, dropping down to 71 on Tuesday and Wednesday nights.

Typically the coolest temperatures hit around 6 a.m., at least in Fresno.

Keeping Cool at Public Libraries

There are options to staying cool, GV Wire reported earlier this week.

And on Friday, Fresno County announced that it’s extending the hours of several branch libraries to help people keep cool during the heat wave.

The Betty Rodriguez, Clovis, Fig Garden, Sunnyside, and Woodward Park Regional libraries and the Central Branch Library will remain open until 8 p.m. Friday through Sunday in July and will keep their regular hours on other days of the week.

The Auberry, Bear Mountain, Caruthers, and San Joaquin Branch libraries will be open until 8 p.m. Friday through Monday, with additional hours and service days the rest of the month.

While Wi-Fi and air conditioning will remain active and restrooms will be open, some branch services such as public computers will not be available during the extended hours.

Cool places will be popular for some time to come. Serrato said the Climate Prediction Center is forecasting the possibility of triple-digit temperatures for at least the next two weeks.