First, obtain an API key from OpenWeather by signing up on their website. Ensure you have the necessary permissions to access the specific weather data you need. Familiarize yourself with their API documentation to understand the endpoints and data formats (typically JSON or XML) available for your data extraction.

Write a Python script to fetch weather data from OpenWeather. Utilize the `requests` library to send HTTP GET requests to the appropriate OpenWeather API endpoint. Parse the JSON response to extract the necessary data fields you want to transfer to Starburst Galaxy.

```python
import requests

api_key = 'YOUR_API_KEY'
city = 'CITY_NAME'
url = f'http://api.openweathermap.org/data/2.5/weather?q={city}&appid={api_key}'

response = requests.get(url)
weather_data = response.json()
```

Transform the extracted data into a CSV format, which is easily ingested by Starburst Galaxy. Utilize Python’s `csv` module to write the data into a CSV file. Ensure your data is structured in a tabular format with headers corresponding to data fields.

```python
import csv

with open('weather_data.csv', mode='w', newline='') as csv_file:
fieldnames = ['city', 'temperature', 'humidity', 'pressure']
writer = csv.DictWriter(csv_file, fieldnames=fieldnames)

writer.writeheader()
writer.writerow({
'city': weather_data['name'],
'temperature': weather_data['main']['temp'],
'humidity': weather_data['main']['humidity'],
'pressure': weather_data['main']['pressure']
})
```

Ensure you have access to a Starburst Galaxy account and have set up your environment. Create a new catalog or schema if necessary to store your incoming data. Familiarize yourself with the Galaxy interface and available features for data ingestion.

Create an external table in Starburst Galaxy to map to your CSV file. This step involves using SQL commands to define table structure and data types that match your CSV file. Access the Starburst Galaxy SQL editor to execute these commands.

```sql
CREATE TABLE weather_data (
city VARCHAR,
temperature DOUBLE,
humidity INTEGER,
pressure INTEGER
)
WITH (
format = 'CSV',
external_location = 's3://your-bucket/weather_data.csv' -- Adjust path as needed
);
```

Transfer the CSV file to a cloud storage service that Starburst Galaxy can access, such as Amazon S3, Google Cloud Storage, or Azure Blob Storage. Ensure the file permissions allow Starburst Galaxy to read the file.

```bash
aws s3 cp weather_data.csv s3://your-bucket/weather_data.csv
```

Finally, use Starburst Galaxy’s SQL editor to query the data from your new table and verify its accuracy. Check for consistency with your original JSON data from OpenWeather and ensure all fields have been populated correctly.

```sql
SELECT FROM weather_data;
```

By following these steps, you can successfully transfer data from OpenWeather to Starburst Galaxy without relying on third-party connectors or integrations.