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 2024-11-04.

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	10% 8% 3 6% 4 4 4 3 4 6% 48%	105334
	Night	13% 9% 3 7% 4 4 4 3 4 6% 45%	102387
Transparency	Day	35% 7% 11% 20% 18% 9%	105087
	Night	39% 8% 13% 20% 14% 6%	102224
Seeing	Day	14% 11% 23% 26% 19% 7%	14961
	Night	14% 5% 14% 34% 29% 4	23968

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	20% 18% 5% 13% 8% 6% 5% 4 5% 4 12%	2539
	11th to 20th	Day	30% 15% 4 10% 5% 4 5% 3 4 4 16%	2736
	21st to end	Day	29% 13% 3 9% 5% 4 4 4 5% 7% 18%	3146
February	1st to 10th	Day	15% 13% 4 10% 6% 6% 5% 5% 7% 6% 23%	1710
	11th to 20th	Day	15% 13% 4 10% 6% 5% 4 4 5% 7% 27%	1665
	21st to end	Day	16% 17% 5% 10% 6% 4 4 4 5% 5% 23%	1504
March	1st to 10th	Day	17% 17% 5% 11% 5% 4 4 2 5% 5% 23%	3403
	11th to 20th	Day	12% 10% 3 7% 4 4 4 3 5% 6% 42%	3490
	21st to end	Day	18% 14% 5% 10% 6% 5% 5% 4 6% 7% 20%	3841
April	1st to 10th	Day	15% 12% 4 10% 7% 5% 5% 5% 4 7% 26%	2280
	11th to 20th	Day	16% 12% 4 8% 6% 4 4 3 5% 7% 30%	2249
	21st to end	Day	11% 10% 4 8% 5% 4 4 4 6% 8% 37%	2418
May	1st to 10th	Day	11% 9% 3 7% 4 4 4 3 5% 6% 44%	4127
	11th to 20th	Day	6% 4 2 4 3 3 4 2 4 5% 63%	4377
	21st to end	Day	8% 5% 2 4 4 3 4 3 6% 8% 53%	4813
June	1st to 10th	Day	10% 8% 3 6% 4 4 3 3 5% 8% 45%	2660
	11th to 20th	Day	6% 5% 2 5% 4 4 5% 3 5% 6% 55%	2660
	21st to end	Day	4 3 1 3 2 2 3 2 4 5% 70%	2660
July	1st to 10th	Day	1 1 1 1 1 1 1 2 2 88%	4420
	11th to 20th	Day	2 2 1 2 2 2 2 1 3 3 80%	4420
	21st to end	Day	1 1 1 1 1 1 1 2 3 86%	4502
August	1st to 10th	Day	2 2 1 3 2 2 3 2 3 4 77%	4091
	11th to 20th	Day	2 2 1 3 2 2 3 2 3 5% 75%	4026
	21st to end	Day	2 2 1 4 2 2 2 2 3 4 76%	4252
September	1st to 10th	Day	2 3 1 2 2 2 3 2 3 6% 74%	2280
	11th to 20th	Day	5% 4 2 5% 3 3 4 3 5% 7% 58%	2237
	21st to end	Day	7% 4 2 5% 3 3 3 3 5% 8% 58%	2024
October	1st to 10th	Day	5% 4 1 5% 3 3 3 2 3 5% 66%	3180
	11th to 20th	Day	8% 8% 3 7% 5% 4 5% 4 6% 9% 42%	3161
	21st to end	Day	13% 10% 3 8% 5% 5% 5% 4 6% 8% 33%	3448
November	1st to 10th	Day	20% 11% 5% 10% 6% 5% 5% 3 5% 6% 23%	1733
	11th to 20th	Day	18% 13% 4 10% 6% 5% 6% 4 7% 8% 20%	1520
	21st to end	Day	16% 13% 4 10% 6% 6% 5% 3 4 6% 24%	1520
December	1st to 10th	Day	15% 11% 5% 10% 7% 5% 4 3 5% 7% 28%	1520
	11th to 20th	Day	21% 12% 4 14% 7% 5% 5% 4 6% 7% 16%	1928
	21st to end	Day	22% 18% 6% 14% 8% 6% 4 3 4 5% 10%	2794
January	1st to 10th	Night	21% 17% 5% 12% 7% 6% 5% 3 5% 5% 13%	4406
	11th to 20th	Night	26% 15% 5% 11% 5% 6% 3 2 3 4 19%	4228
	21st to end	Night	32% 13% 4 8% 4 3 3 3 4 5% 20%	4521
February	1st to 10th	Night	15% 13% 4 7% 5% 4 5% 4 5% 7% 29%	2470
	11th to 20th	Night	17% 13% 5% 8% 4 4 4 3 5% 6% 30%	2402
	21st to end	Night	14% 15% 4 8% 4 5% 5% 3 5% 7% 29%	1948
March	1st to 10th	Night	19% 17% 4 9% 5% 4 4 4 5% 6% 23%	3467
	11th to 20th	Night	12% 10% 2 7% 4 3 3 2 4 6% 46%	3490
	21st to end	Night	15% 14% 5% 11% 6% 6% 5% 4 5% 6% 21%	3810
April	1st to 10th	Night	15% 15% 3 8% 6% 5% 5% 3 5% 5% 30%	1900
	11th to 20th	Night	11% 13% 3 8% 5% 3 4 4 4 6% 38%	1879
	21st to end	Night	12% 9% 3 7% 4 4 4 5% 6% 7% 38%	1758
May	1st to 10th	Night	12% 9% 3 6% 4 3 3 2 4 7% 47%	2842
	11th to 20th	Night	5% 4 1 5% 3 3 3 3 4 6% 64%	2516
	21st to end	Night	8% 5% 2 5% 3 3 3 2 5% 7% 57%	2762
June	1st to 10th	Night	10% 7% 2 5% 4 5% 4 3 6% 6% 49%	1520
	11th to 20th	Night	6% 4 1 3 3 3 4 3 5% 6% 61%	1520
	21st to end	Night	4 3 1 2 2 2 3 2 2 4 77%	1520
July	1st to 10th	Night	1 1 1 1 1 1 1 2 3 88%	2540
	11th to 20th	Night	2 1 1 2 1 2 1 1 3 3 83%	2540
	21st to end	Night	1 1 1 1 1 2 2 3 3 86%	3043
August	1st to 10th	Night	1 1 1 2 2 2 2 2 3 4 80%	2848
	11th to 20th	Night	1 2 1 2 1 2 3 2 4 6% 77%	2812
	21st to end	Night	3 2 1 3 2 2 2 2 3 3 77%	3422
September	1st to 10th	Night	2 1 1 2 1 2 2 1 4 4 81%	1900
	11th to 20th	Night	4 3 1 3 3 3 3 3 5% 6% 67%	1939
	21st to end	Night	7% 4 2 4 3 3 3 3 4 6% 62%	2156
October	1st to 10th	Night	4 3 2 4 2 2 2 2 3 4 72%	3800
	11th to 20th	Night	8% 6% 2 6% 4 4 3 3 6% 7% 51%	3777
	21st to end	Night	13% 11% 4 9% 5% 5% 5% 4 6% 6% 33%	4121
November	1st to 10th	Night	18% 11% 4 8% 6% 5% 5% 3 4 6% 30%	2412
	11th to 20th	Night	18% 10% 4 10% 6% 6% 5% 4 6% 8% 25%	2660
	21st to end	Night	17% 10% 3 8% 5% 4 5% 3 5% 7% 32%	2660
December	1st to 10th	Night	17% 11% 4 7% 5% 4 4 4 5% 7% 33%	2660
	11th to 20th	Night	22% 15% 4 10% 5% 4 4 3 5% 7% 19%	3276
	21st to end	Night	20% 16% 5% 12% 7% 6% 5% 3 4 5% 17%	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	55% 9% 13% 15% 6% 1	2280
	11th to 20th	Day	50% 8% 17% 14% 8% 4	2252
	21st to end	Day	43% 9% 18% 19% 10% 1	2418
May	1st to 10th	Day	38% 8% 13% 24% 14% 2	4127
	11th to 20th	Day	23% 6% 11% 31% 26% 4	4380
	21st to end	Day	29% 8% 23% 33% 8%	4814
June	1st to 10th	Day	37% 7% 15% 29% 12% 1	2660
	11th to 20th	Day	29% 7% 15% 33% 15% 2	2660
	21st to end	Day	18% 3 12% 34% 25% 7%	2660
July	1st to 10th	Day	7% 2 6% 16% 24% 46%	4351
	11th to 20th	Day	11% 2 5% 15% 32% 36%	4345
	21st to end	Day	7% 1 5% 21% 46% 20%	4360
August	1st to 10th	Day	13% 2 6% 20% 39% 19%	4076
	11th to 20th	Day	12% 3 8% 35% 31% 12%	4065
	21st to end	Day	14% 3 7% 31% 34% 10%	4251
September	1st to 10th	Day	12% 4 6% 25% 33% 20%	2280
	11th to 20th	Day	23% 6% 13% 26% 23% 8%	2237
	21st to end	Day	24% 6% 10% 27% 22% 11%	2024
October	1st to 10th	Day	21% 6% 10% 18% 25% 22%	3180
	11th to 20th	Day	35% 6% 18% 24% 14% 3	3161
	21st to end	Day	43% 7% 12% 19% 16% 3	3448
November	1st to 10th	Day	56% 10% 12% 12% 9% 1	1733
	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% 15% 6%	1900
	11th to 20th	Night	45% 10% 19% 17% 6% 3	1879
	21st to end	Night	41% 11% 21% 21% 6% 1	1758
May	1st to 10th	Night	34% 11% 19% 23% 12% 1	2842
	11th to 20th	Night	21% 8% 14% 42% 14% 1	2516
	21st to end	Night	28% 8% 32% 29% 3	2762
June	1st to 10th	Night	36% 8% 18% 31% 7%	1520
	11th to 20th	Night	25% 6% 20% 35% 14% 1	1520
	21st to end	Night	15% 4 14% 41% 21% 5%	1520
July	1st to 10th	Night	6% 2 7% 18% 25% 42%	2500
	11th to 20th	Night	9% 2 4 19% 35% 33%	2492
	21st to end	Night	6% 1 6% 24% 47% 16%	2948
August	1st to 10th	Night	11% 2 7% 24% 47% 10%	2839
	11th to 20th	Night	10% 3 13% 39% 25% 10%	2839
	21st to end	Night	13% 3 8% 33% 35% 7%	3422
September	1st to 10th	Night	9% 2 7% 30% 34% 17%	1900
	11th to 20th	Night	18% 5% 16% 32% 22% 6%	1939
	21st to end	Night	23% 5% 12% 27% 21% 12%	2156
October	1st to 10th	Night	18% 4 10% 21% 28% 18%	3800
	11th to 20th	Night	31% 6% 17% 31% 12% 3	3777
	21st to end	Night	47% 7% 11% 19% 11% 4	4121
November	1st to 10th	Night	52% 9% 13% 12% 11% 3	2412
	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	460
	11th to 20th	Day	19% 18% 26% 21% 12% 3	452
	21st to end	Day	16% 18% 27% 22% 12% 5%	460
May	1st to 10th	Day	16% 16% 27% 21% 16% 5%	463
	11th to 20th	Day	17% 13% 25% 22% 17% 6%	488
	21st to end	Day	14% 12% 26% 26% 16% 6%	529
June	1st to 10th	Day	13% 13% 27% 24% 17% 7%	490
	11th to 20th	Day	10% 17% 33% 24% 12% 5%	490
	21st to end	Day	4 9% 29% 32% 18% 9%	490
July	1st to 10th	Day	3 8% 26% 37% 19% 8%	486
	11th to 20th	Day	2 6% 31% 35% 18% 8%	484
	21st to end	Day	1 4 26% 37% 22% 9%	531
August	1st to 10th	Day	3 5% 23% 34% 24% 10%	487
	11th to 20th	Day	1 8% 22% 32% 25% 12%	477
	21st to end	Day	5% 6% 23% 30% 26% 10%	539
September	1st to 10th	Day	4 6% 21% 30% 28% 11%	490
	11th to 20th	Day	9% 7% 23% 29% 25% 9%	490
	21st to end	Day	8% 9% 20% 29% 25% 9%	490
October	1st to 10th	Day	11% 9% 18% 26% 24% 12%	490
	11th to 20th	Day	12% 9% 18% 22% 27% 11%	490
	21st to end	Day	19% 10% 19% 24% 17% 11%	539
November	1st to 10th	Day	18% 12% 16% 29% 18% 8%	331
	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% 31% 19% 2	760
	11th to 20th	Night	15% 10% 19% 32% 21% 3	751
	21st to end	Night	16% 6% 16% 32% 28% 2	618
May	1st to 10th	Night	11% 7% 14% 37% 28% 4	565
	11th to 20th	Night	8% 6% 14% 34% 35% 3	374
	21st to end	Night	10% 4 17% 35% 31% 4	411
June	1st to 10th	Night	11% 4 12% 36% 35% 3	380
	11th to 20th	Night	7% 4 15% 41% 31% 2	380
	21st to end	Night	6% 1 9% 38% 44% 2	380
July	1st to 10th	Night	2 1 7% 34% 53% 2	370
	11th to 20th	Night	2 1 7% 42% 46% 2	368
	21st to end	Night	2 1 4 29% 55% 9%	584
August	1st to 10th	Night	2 1 3 29% 53% 11%	567
	11th to 20th	Night	2 1 4 28% 56% 10%	564
	21st to end	Night	3 1 11% 34% 44% 7%	786
September	1st to 10th	Night	2 2 12% 31% 48% 5%	760
	11th to 20th	Night	4 2 13% 29% 42% 9%	760
	21st to end	Night	8% 4 10% 34% 36% 9%	760
October	1st to 10th	Night	9% 2 13% 36% 34% 6%	760
	11th to 20th	Night	12% 3 10% 36% 34% 6%	760
	21st to end	Night	15% 4 13% 34% 27% 7%	836
November	1st to 10th	Night	19% 7% 13% 36% 21% 4	754
	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 2024-11-01 19:47:40. Version ac07

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