Long Island weather: Cloudy with highs around 70; rain tomorrow

Wednesday’s clouds may partly block the sun, but no rain is anticipated until shortly before dawn Thursday — and while showers may stick around Friday, the weekend should be clear, the forecasters said.

The daytime high on Wednesday should top out at 70 degrees. Thursday’s high will climb to 63 degrees.

Temperatures during the day Friday should rise to about 79 degrees and then slowly increase over the weekend, reaching the low to mid-80s by the middle of next week, the National Weather Service said.

Some sections of the tri-state area, especially away from coastal breezes, may see higher temperatures this weekend. Highs in the low 90s are possible, thanks to a southwesterly flow from West Virginia, the weather service said.

Rainy Thursday ahead

Thursday’s rain will develop from a low pressure system that will swing into the northeast and Lower Great Lakes from the Lower Mississippi Valley, according to the weather service's Weather Prediction Center.

Rain arrives with low pressure systems because their warm air rises, allowing vapors to condense into clouds and rain drops. Blue skies stem from high pressure systems, as their cool air dries as it falls to Earth.

"At the same time, an associated warm front to its east will lift northward and usher in a warm and humid airmass to nearly the entire East Coast," the prediction center said.

But Long Island is not under the threat of the severe weather, including isolated tornadoes, that a slow-moving cold front may bring from Virginia to Maryland to southeast Pennsylvania.

Thursday’s chances of rain after 4 a.m. are 60%. During the day, those odds will rise to 80%, and the showers and possible thunderstorms could arrive in waves, according to the weather service.

"The rain intensity will become more steady and moderate and potentially heavy at times for Thursday for the morning into early afternoon," the weather service said.

It added, "Another round of rain showers will be likely at night."

As much as 1¾ of an inch of rain may fall by Thursday night, with the coasts likely to get the heaviest rain, the weather service estimated.

"Minor flooding will be possible with showers and thunderstorms Thursday into Thursday night, especially for any low-lying and urban areas with poor drainage," the weather service said.

Friday’s odds of rain are 60%, but showers should be concentrated in the earlier part of the day and less than a tenth of an inch of rainfall is expected — though thunderstorms may deliver more.

"Actually with some more sun expected Friday, there will be a more conducive environment for thunderstorms with warmer temperatures, and with the same humidity levels generally from the day before, more instability," the weather service explained.

The Saturday to Tuesday stretch should be consistently sunny, with daytime temperatures reaching fairly usual levels for late spring. Nightime lows should be in the low 60s.