(CNN)-- A near-normal Atlantic hurricane season is expected this year, with nine to 15 named storms and four to eight hurricanes, the National Oceanic and Atmospheric Administration announced Thursday.
Of those four to eight hurricanes, NOAA expects one to three to be major. The Atlantic's six-month season begins June 1, although it got off to an early start this year, with Tropical Storm Alberto moving through the Atlantic off the U.S. East Coast last week.
NOAA also said it predicts a near-normal season for the Eastern Pacific, estimating a 70% chance of 12 to 18 named storms – with five to nine hurricanes, of which two to five would be major – for that area. The Eastern Pacific's season is May 15 to November 30.
A major hurricane, designated as Category 3 or greater, has winds of well above 100 mph. The weakest hurricanes have top sustained winds of at least 74 mph, and named storms have top winds of at least 39 mph.
NOAA officials said uncertainty over whether the El Nino weather pattern will form made it difficult to be more precise in predicting the Atlantic storm season.
"If (El Nino) develops by late summer to early fall ... conditions could be less conducive for hurricane formation and intensification during the peak months (August to October) of the season, possibly shifting the activity toward the lower end of the predicted range,” said Gerry Bell, lead seasonal hurricane forecaster at NOAA’s Climate Prediction Center.
The forecasts do not predict how many of the storms will reach land.
Thursday's predictions came as a strengthening Hurricane Bud, churning in the Pacific, appeared poised to bring heavy rain to coastal southwestern Mexico.
It is extremely rare for an Eastern Pacific hurricane to affect the U.S. mainland, though some do have an influence on Hawaii.
Tropical Storm Alberto broke up in the Atlantic this week and another tropical depression was causing heavy rainfall in southern Florida, Bell said. However, he said the early storms were no harbinger of a more active season than normal.
For the Atlantic, a normal season would produce 12 named storms, including six hurricanes and three major hurricanes. Last year saw 19 named storms in the Atlantic.
The Eastern Pacific's average season produces 15 named storms, with eight hurricanes and four major hurricanes, according to NOAA.