Grants Pass
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Grants Pass clear sky chart from 2005-11-06 to 2024-04-10.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	13% 9% 3 6% 5% 3 4 4 4 6% 42%	83258
	Night	14% 10% 3 6% 5% 3 4 4 4 6% 40%	85613
Transparency	Day	40% 8% 12% 19% 15% 5%	82971
	Night	42% 9% 13% 19% 12% 4	85422
Seeing	Day	14% 11% 22% 26% 19% 7%	14130
	Night	15% 5% 14% 34% 29% 4	23334

By Month

Percentage Cloud Cover SW (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	21% 17% 5% 12% 9% 5% 5% 5% 5% 4 12%	2539
	11th to 20th	Day	31% 15% 4 9% 6% 3 5% 4 4 4 16%	2736
	21st to end	Day	29% 12% 4 7% 6% 3 4 5% 5% 7% 18%	3146
February	1st to 10th	Day	15% 12% 4 9% 7% 5% 6% 6% 7% 6% 23%	1710
	11th to 20th	Day	15% 12% 5% 9% 6% 4 4 5% 5% 7% 27%	1665
	21st to end	Day	17% 16% 5% 9% 7% 4 5% 4 5% 5% 23%	1504
March	1st to 10th	Day	18% 16% 6% 10% 7% 4 4 4 4 6% 23%	3403
	11th to 20th	Day	12% 9% 3 6% 5% 3 4 4 5% 6% 42%	3490
	21st to end	Day	18% 14% 5% 9% 7% 4 5% 5% 6% 7% 20%	3841
April	1st to 10th	Day	15% 11% 5% 9% 8% 4 5% 5% 4 7% 26%	2270
	11th to 20th	Day	17% 11% 4 7% 6% 3 5% 4 5% 7% 30%	2129
	21st to end	Day	11% 10% 4 7% 6% 3 4 4 5% 7% 39%	2290
May	1st to 10th	Day	9% 8% 3 6% 5% 3 4 4 5% 7% 47%	2344
	11th to 20th	Day	11% 7% 3 6% 6% 3 6% 5% 5% 7% 42%	2477
	21st to end	Day	14% 7% 3 5% 5% 3 4 4 6% 8% 41%	2723
June	1st to 10th	Day	11% 7% 3 6% 4 3 4 4 5% 8% 45%	2520
	11th to 20th	Day	6% 5% 2 5% 5% 3 5% 4 5% 6% 55%	2520
	21st to end	Day	5% 3 1 2 3 2 3 2 3 6% 69%	2520
July	1st to 10th	Day	2 2 1 2 2 2 2 2 3 4 79%	2520
	11th to 20th	Day	3 2 1 2 2 1 2 2 3 4 78%	2520
	21st to end	Day	2 2 1 2 2 1 2 2 2 4 82%	2580
August	1st to 10th	Day	2 2 1 2 2 1 2 3 3 5% 77%	2328
	11th to 20th	Day	1 2 1 2 2 1 2 2 3 5% 78%	2298
	21st to end	Day	2 2 1 2 2 1 2 2 3 4 77%	2422
September	1st to 10th	Day	2 3 1 2 2 1 3 3 3 6% 74%	2160
	11th to 20th	Day	5% 4 1 4 4 2 4 4 5% 7% 59%	2120
	21st to end	Day	7% 4 2 4 4 2 3 4 5% 8% 56%	1918
October	1st to 10th	Day	9% 5% 2 5% 5% 2 4 4 4 7% 53%	1800
	11th to 20th	Day	11% 7% 3 7% 6% 3 4 5% 6% 7% 43%	1800
	21st to end	Day	14% 10% 4 6% 6% 4 4 4 5% 7% 37%	1980
November	1st to 10th	Day	20% 11% 5% 9% 7% 4 6% 4 5% 6% 24%	1703
	11th to 20th	Day	18% 12% 5% 9% 7% 4 6% 5% 7% 8% 21%	1520
	21st to end	Day	17% 12% 5% 9% 8% 5% 6% 5% 4 6% 24%	1520
December	1st to 10th	Day	15% 10% 6% 8% 8% 4 5% 4 5% 7% 29%	1520
	11th to 20th	Day	22% 11% 4 12% 8% 4 5% 5% 6% 7% 16%	1928
	21st to end	Day	22% 17% 6% 12% 10% 4 5% 4 4 5% 10%	2794
January	1st to 10th	Night	21% 16% 5% 11% 9% 4 6% 5% 5% 5% 13%	4406
	11th to 20th	Night	27% 14% 5% 10% 6% 4 4 3 3 4 19%	4228
	21st to end	Night	32% 13% 4 7% 5% 3 3 3 4 5% 20%	4521
February	1st to 10th	Night	15% 12% 5% 6% 6% 3 5% 5% 5% 8% 29%	2470
	11th to 20th	Night	18% 13% 5% 7% 5% 3 4 4 5% 6% 31%	2402
	21st to end	Night	15% 13% 4 7% 5% 3 6% 5% 5% 7% 29%	1948
March	1st to 10th	Night	19% 16% 4 8% 6% 3 5% 5% 5% 6% 23%	3467
	11th to 20th	Night	13% 9% 3 7% 5% 2 4 3 4 6% 46%	3490
	21st to end	Night	15% 13% 6% 10% 8% 4 5% 6% 5% 6% 21%	3810
April	1st to 10th	Night	15% 14% 4 7% 6% 4 5% 5% 5% 6% 30%	1900
	11th to 20th	Night	11% 12% 4 8% 6% 2 4 4 4 6% 38%	1779
	21st to end	Night	13% 9% 3 6% 5% 3 4 6% 6% 8% 39%	1666
May	1st to 10th	Night	8% 7% 3 5% 4 3 4 4 5% 7% 50%	1616
	11th to 20th	Night	8% 6% 2 7% 5% 4 5% 5% 6% 8% 44%	1416
	21st to end	Night	11% 5% 3 5% 6% 3 4 3 5% 9% 47%	1552
June	1st to 10th	Night	10% 6% 2 4 4 3 4 4 5% 6% 49%	1440
	11th to 20th	Night	6% 4 2 3 3 3 4 3 5% 6% 61%	1440
	21st to end	Night	4 3 1 1 2 2 2 3 2 4 76%	1440
July	1st to 10th	Night	3 2 1 1 2 1 2 2 3 5% 78%	1440
	11th to 20th	Night	3 1 1 2 2 1 2 2 3 4 80%	1440
	21st to end	Night	1 1 1 1 1 2 2 3 86%	1735
August	1st to 10th	Night	2 1 2 2 1 3 3 3 5% 78%	1611
	11th to 20th	Night	1 2 1 2 1 1 2 2 3 4 81%	1602
	21st to end	Night	2 1 1 2 2 2 2 1 3 3 82%	1932
September	1st to 10th	Night	2 1 1 1 2 1 2 2 4 3 81%	1800
	11th to 20th	Night	4 3 1 3 3 2 3 3 5% 6% 68%	1836
	21st to end	Night	7% 4 2 3 4 2 3 3 4 6% 61%	2042
October	1st to 10th	Night	7% 4 2 3 4 2 4 3 4 7% 61%	2160
	11th to 20th	Night	11% 6% 2 5% 4 3 3 4 5% 6% 53%	2160
	21st to end	Night	14% 8% 2 5% 4 3 4 4 5% 6% 44%	2376
November	1st to 10th	Night	18% 10% 5% 7% 7% 4 5% 4 4 6% 30%	2370
	11th to 20th	Night	18% 10% 4 9% 7% 4 6% 5% 5% 8% 25%	2660
	21st to end	Night	17% 10% 3 7% 6% 3 5% 4 5% 7% 32%	2660
December	1st to 10th	Night	18% 9% 5% 7% 5% 3 4 4 4 7% 33%	2660
	11th to 20th	Night	22% 14% 5% 9% 6% 4 4 4 5% 7% 19%	3276
	21st to end	Night	20% 15% 5% 11% 8% 4 5% 4 4 5% 18%	4862

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	65% 15% 10% 8% 2 1	2539
	11th to 20th	Day	65% 9% 8% 10% 4 3	2736
	21st to end	Day	60% 11% 11% 11% 5% 2	3146
February	1st to 10th	Day	54% 11% 14% 14% 7% 1	1710
	11th to 20th	Day	51% 12% 12% 17% 6% 2	1674
	21st to end	Day	58% 11% 10% 13% 7% 1	1504
March	1st to 10th	Day	60% 8% 12% 16% 3	3403
	11th to 20th	Day	39% 9% 12% 19% 21%	3490
	21st to end	Day	57% 13% 15% 13% 3	3841
April	1st to 10th	Day	56% 9% 14% 14% 6% 1	2270
	11th to 20th	Day	51% 8% 16% 13% 7% 4	2132
	21st to end	Day	43% 8% 18% 19% 11% 1	2290
May	1st to 10th	Day	37% 6% 17% 26% 12% 1	2344
	11th to 20th	Day	40% 7% 15% 25% 10% 2	2480
	21st to end	Day	42% 7% 20% 23% 7%	2724
June	1st to 10th	Day	37% 7% 15% 29% 11%	2520
	11th to 20th	Day	30% 7% 15% 33% 14% 2	2520
	21st to end	Day	19% 4 12% 34% 24% 7%	2520
July	1st to 10th	Day	12% 3 10% 28% 30% 16%	2451
	11th to 20th	Day	12% 3 6% 22% 36% 20%	2445
	21st to end	Day	10% 2 4 23% 46% 16%	2437
August	1st to 10th	Day	12% 3 10% 33% 31% 11%	2312
	11th to 20th	Day	11% 3 9% 26% 38% 13%	2298
	21st to end	Day	12% 3 9% 28% 37% 11%	2422
September	1st to 10th	Day	12% 4 6% 25% 33% 20%	2160
	11th to 20th	Day	23% 6% 12% 26% 25% 9%	2120
	21st to end	Day	25% 6% 11% 25% 21% 11%	1918
October	1st to 10th	Day	29% 8% 13% 18% 20% 11%	1800
	11th to 20th	Day	37% 8% 13% 19% 17% 6%	1800
	21st to end	Day	43% 9% 13% 13% 16% 6%	1980
November	1st to 10th	Day	56% 10% 11% 12% 10% 1	1703
	11th to 20th	Day	54% 11% 13% 11% 8% 3	1520
	21st to end	Day	53% 12% 10% 9% 11% 4	1520
December	1st to 10th	Day	50% 9% 12% 16% 11% 1	1520
	11th to 20th	Day	60% 14% 12% 10% 5%	1928
	21st to end	Day	67% 15% 7% 8% 2 1	2794
January	1st to 10th	Night	64% 14% 11% 7% 3 1	4406
	11th to 20th	Night	62% 10% 9% 11% 4 3	4228
	21st to end	Night	63% 8% 9% 12% 7% 2	4521
February	1st to 10th	Night	50% 10% 15% 15% 8% 1	2470
	11th to 20th	Night	51% 9% 13% 19% 6% 1	2404
	21st to end	Night	49% 12% 16% 16% 5% 2	1948
March	1st to 10th	Night	56% 8% 15% 17% 3	3467
	11th to 20th	Night	37% 9% 14% 24% 14% 3	3490
	21st to end	Night	54% 15% 17% 11% 2	3810
April	1st to 10th	Night	54% 8% 17% 16% 6%	1900
	11th to 20th	Night	45% 10% 18% 17% 6% 3	1779
	21st to end	Night	41% 10% 21% 21% 6% 1	1666
May	1st to 10th	Night	33% 9% 21% 27% 10% 1	1616
	11th to 20th	Night	37% 9% 20% 26% 6% 2	1416
	21st to end	Night	36% 9% 26% 24% 5%	1552
June	1st to 10th	Night	36% 8% 19% 31% 6%	1440
	11th to 20th	Night	25% 7% 21% 35% 12%	1440
	21st to end	Night	15% 4 14% 41% 21% 4	1440
July	1st to 10th	Night	11% 3 12% 32% 27% 14%	1400
	11th to 20th	Night	11% 3 5% 29% 38% 15%	1392
	21st to end	Night	7% 1 4 27% 47% 14%	1639
August	1st to 10th	Night	11% 3 11% 38% 30% 7%	1602
	11th to 20th	Night	8% 3 9% 33% 37% 9%	1602
	21st to end	Night	9% 3 9% 33% 37% 9%	1932
September	1st to 10th	Night	9% 3 8% 29% 34% 17%	1800
	11th to 20th	Night	17% 5% 16% 32% 23% 7%	1836
	21st to end	Night	24% 6% 12% 26% 20% 12%	2042
October	1st to 10th	Night	25% 6% 14% 23% 23% 9%	2160
	11th to 20th	Night	31% 7% 15% 22% 21% 5%	2160
	21st to end	Night	39% 9% 13% 18% 15% 7%	2376
November	1st to 10th	Night	52% 9% 13% 12% 11% 3	2370
	11th to 20th	Night	54% 9% 14% 12% 8% 2	2660
	21st to end	Night	48% 9% 13% 14% 12% 4	2660
December	1st to 10th	Night	47% 9% 12% 18% 12% 1	2660
	11th to 20th	Night	60% 9% 12% 14% 5% 1	3276
	21st to end	Night	59% 15% 12% 10% 3 1	4862

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	32% 13% 19% 19% 12% 5%	180
	11th to 20th	Day	30% 8% 13% 23% 15% 12%	298
	21st to end	Day	22% 9% 19% 22% 20% 8%	407
February	1st to 10th	Day	18% 11% 18% 25% 24% 4	370
	11th to 20th	Day	28% 12% 20% 22% 14% 5%	365
	21st to end	Day	26% 15% 18% 24% 14% 3	351
March	1st to 10th	Day	27% 16% 22% 21% 12% 3	460
	11th to 20th	Day	20% 13% 20% 23% 19% 4	460
	21st to end	Day	23% 18% 21% 23% 14% 1	506
April	1st to 10th	Day	22% 15% 25% 23% 12% 3	457
	11th to 20th	Day	20% 19% 26% 20% 12% 3	412
	21st to end	Day	16% 18% 27% 22% 13% 5%	420
May	1st to 10th	Day	16% 16% 26% 21% 16% 5%	423
	11th to 20th	Day	19% 14% 23% 22% 16% 6%	448
	21st to end	Day	15% 12% 25% 25% 16% 7%	485
June	1st to 10th	Day	13% 13% 26% 24% 17% 7%	450
	11th to 20th	Day	10% 15% 33% 25% 12% 5%	450
	21st to end	Day	3 9% 28% 32% 20% 8%	450
July	1st to 10th	Day	3 9% 26% 38% 17% 7%	446
	11th to 20th	Day	2 7% 30% 35% 19% 8%	444
	21st to end	Day	1 4 25% 37% 23% 10%	487
August	1st to 10th	Day	3 4 22% 36% 24% 11%	447
	11th to 20th	Day	7% 21% 33% 26% 12%	437
	21st to end	Day	4 6% 24% 30% 26% 9%	495
September	1st to 10th	Day	5% 6% 21% 30% 27% 12%	450
	11th to 20th	Day	8% 6% 22% 29% 25% 9%	450
	21st to end	Day	8% 10% 20% 30% 25% 9%	450
October	1st to 10th	Day	12% 10% 19% 24% 24% 12%	450
	11th to 20th	Day	13% 8% 17% 22% 27% 12%	450
	21st to end	Day	17% 10% 17% 25% 18% 12%	495
November	1st to 10th	Day	17% 12% 16% 29% 18% 8%	319
	11th to 20th	Day	18% 6% 17% 26% 24% 10%	180
	21st to end	Day	19% 6% 14% 30% 21% 9%	180
December	1st to 10th	Day	18% 9% 12% 28% 21% 12%	180
	11th to 20th	Day	30% 3 18% 20% 22% 6%	180
	21st to end	Day	29% 9% 18% 22% 19% 4	198
January	1st to 10th	Night	21% 8% 17% 34% 16% 3	760
	11th to 20th	Night	21% 8% 16% 32% 19% 5%	760
	21st to end	Night	23% 5% 12% 33% 22% 4	836
February	1st to 10th	Night	18% 7% 15% 36% 23% 2	760
	11th to 20th	Night	20% 6% 17% 34% 21% 2	744
	21st to end	Night	18% 9% 19% 36% 17% 1	628
March	1st to 10th	Night	23% 10% 20% 30% 16% 2	760
	11th to 20th	Night	19% 7% 16% 34% 22% 2	760
	21st to end	Night	19% 9% 23% 31% 17%	836
April	1st to 10th	Night	19% 9% 20% 30% 19% 3	760
	11th to 20th	Night	15% 11% 18% 32% 21% 3	711
	21st to end	Night	16% 6% 15% 32% 28% 2	586
May	1st to 10th	Night	10% 7% 14% 36% 29% 4	536
	11th to 20th	Night	8% 6% 14% 34% 35% 3	354
	21st to end	Night	11% 3 17% 35% 31% 4	389
June	1st to 10th	Night	11% 4 13% 36% 35% 3	360
	11th to 20th	Night	8% 4 14% 41% 32% 2	360
	21st to end	Night	6% 1 9% 36% 46% 2	360
July	1st to 10th	Night	2 1 7% 34% 53% 3	350
	11th to 20th	Night	3 1 7% 41% 45% 3	348
	21st to end	Night	2 1 3 29% 56% 9%	553
August	1st to 10th	Night	2 1 3 28% 55% 12%	537
	11th to 20th	Night	2 1 4 25% 58% 10%	534
	21st to end	Night	2 1 11% 35% 44% 7%	744
September	1st to 10th	Night	2 2 12% 31% 48% 5%	720
	11th to 20th	Night	4 2 13% 29% 44% 9%	720
	21st to end	Night	8% 3 10% 34% 35% 9%	720
October	1st to 10th	Night	9% 2 13% 37% 32% 6%	720
	11th to 20th	Night	13% 2 10% 36% 34% 6%	720
	21st to end	Night	15% 4 12% 33% 28% 7%	792
November	1st to 10th	Night	19% 6% 13% 36% 22% 4	740
	11th to 20th	Night	20% 5% 16% 36% 21% 2	760
	21st to end	Night	19% 4 14% 36% 24% 2	760
December	1st to 10th	Night	20% 5% 12% 37% 22% 4	760
	11th to 20th	Night	24% 7% 13% 34% 19% 3	760
	21st to end	Night	25% 7% 20% 33% 12% 2	836

Page generated at 2024-04-07 06:28:12. Version ac07

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