Boyd’s Bible Dictionary:

The early rains of Palestine fall in October, in time for seeding; the later, in April, in time for fruits

Concise Bible Dictionary:

Palestine differed from Egypt in that its vegetation was dependent on the rain from heaven, instead of having to be watered from the river. Rain fell regularly except when God withheld it in chastisement (Deut. 11:11-1711But the land, whither ye go to possess it, is a land of hills and valleys, and drinketh water of the rain of heaven: 12A land which the Lord thy God careth for: the eyes of the Lord thy God are always upon it, from the beginning of the year even unto the end of the year. 13And it shall come to pass, if ye shall hearken diligently unto my commandments which I command you this day, to love the Lord your God, and to serve him with all your heart and with all your soul, 14That I will give you the rain of your land in his due season, the first rain and the latter rain, that thou mayest gather in thy corn, and thy wine, and thine oil. 15And I will send grass in thy fields for thy cattle, that thou mayest eat and be full. 16Take heed to yourselves, that your heart be not deceived, and ye turn aside, and serve other gods, and worship them; 17And then the Lord's wrath be kindled against you, and he shut up the heaven, that there be no rain, and that the land yield not her fruit; and lest ye perish quickly from off the good land which the Lord giveth you. (Deuteronomy 11:11‑17)). We read of the “early rain” and the “latter rain.” The early rain was connected with the sowing of seed; the month Bul signifies “rain,” which agrees with about our October; and the latter rain in spring (about our February). By recent statistics the seasons appear to have somewhat altered, and most rain now falls from November to March inclusive. It is also judged that the cutting down of trees to make charcoal has affected the fall of rain in some districts.
The temperature is in degrees of Fahrenheit. The rain in inches. The rain fell at Jerusalem on 65 days only in the year, and at Tiberias on 67 only. The most prevalent winds during the year were West, South West, and North West. Jerusalem is about 2,500 feet above the Mediterranean Sea, and Tiberias about 652 below the sea. From the “ Quarterly Statements” of the Palestine Exploration Fund.