Vog, cool nights and mornings, and muggy days are expected this weekend as a weather system approaches the islands and winds shift southerly.

The National Weather Service expects the northeast trade winds to shift to Kona winds from the south today, bringing volcanic haze from the Big Island up to Oahu and other western islands.

Overnight lows are expected to drop into the low 60s in many areas and muggy conditions are expected Sunday through Tuesday, when the trade winds are scheduled to return.

The weather for the marathon Sunday should start off cool at the 5 a.m. start and then become muggy and hazy through the morning and afternoon. Winds are expected to be light.

Forecasters say there’s a chance of afternoon showers this weekend from the humid conditions and daytime heating, with the greatest likelihood of showers on the Big Island.

Trade winds are expected to return on Tuesday.

The respite from the Kona weather will be brief however.

Forecasters expect another weather system to move over the islands on Thursday and Kona winds will again bring muggy, voggy weather to Honolulu.