Polo threatens storm surge, high winds and heavy rain along Mexico's Pacific coast, while Nolo drifts further from the Hawaiian Islands.
Nolo is moving away from the islands but continues to bring rain and flooding risks, while Polo approaches Mexico's Pacific coast.
Officials warned the intensifying storm could bring powerful winds and flash flooding even as it passed by the islands.
Forecasters expect the storm to slow and strengthen into a major hurricane near the Big Island this weekend, worsening flood risk in already saturated areas.
A report from Scientific American sets out the main available details, with claims kept attributed to their sources.
Forecasters say up to 40 million people across multiple US states could be affected by the early-season storm, as three hurricanes churn simultaneously in the Pacific.
Southwestern Mexico braced for heavy rain after Polo strengthened into a major hurricane, while forecasters warn a separate storm could bring catastrophic flooding to Hawaii.
Heavy rain and extreme surf are forecast as the storm approaches areas still recovering from previous weather events.
Forecasters say the storm could dump up to 25 inches of rain and generate large coastal waves even as it is expected to pass west of the islands.
Hurricane Lowell brought torrential rain and high winds to Hawaii, leaving about 30,000 customers without power, according to Al Jazeera.
Hurricane Lowell caused significant damage on Hawaii's western islands without making a direct hit, downing trees and knocking out power on Kauai, according to the Guardian.
Residents of Hawaii's western islands began surveying damage after Hurricane Lowell caused widespread power outages and flooding, according to the Guardian.
Hurricane Lowell's fierce winds and heavy rain struck Hawaii's western islands, cutting power widely, uprooting trees and damaging coastal roads, according to Sky News Arabia.
Kauai and Ni'ihau are under hurricane warning as damaging winds and heavy rains affect the state's western islands.
Nearly all residents on Hawaii's island of Kauai lost power Tuesday as Hurricane Lowell brought fierce winds and heavy rains.