Cloud cover and thunderstorms are threatening to spoil the show for millions of people hoping to get a glimpse of the solar eclipse as it passes over much of the United States on the "Path of Totality" on Monday, according to reports.

Severe thunderstorms are forecast for parts of the Southern Plains and the Lower Mississippi Valley, which are in the path of totality, and could obscure viewing of the celestial phenomenon, CNN reported. 

The Path of Totality, when the moon fully blocks the sun, will occur along a 100-mile wide stretch from Texas to Maine, giving people in Dallas, Indianapolis, Cleveland and Buffalo, N.Y., prime seats. 

But nasty weather is predicted for parts of Texas, Oklahoma, Arkansas and Louisiana on Monday, including high winds, hail, drenching rain and even a possible tornado, according to the Storm Prediction Network, CNN reported. 

The good news is that the storms are expected to develop later in the day, which could give eclipse-watchers a window Monday afternoon to view totality. 

But people stuck in traffic in those regions after the viewing could be in store for heavy downpours, the report said. 

In contrast, a high-pressure system is developing in the Northeast that could bring cloudless skies, giving people in Maine, Vermont and New Hampshire the best viewing opportunities.